The Medical-Grade Skincare Ingredient Encyclopedia (Canada 2026): Every Active Explained, With Effective Concentrations, pH, Pairings and Canadian Limits

Most skincare fails for one of three reasons: the right ingredient at the wrong concentration, the right ingredient at the wrong pH, or two right ingredients layered in the wrong order. This encyclopedia exists so you never have to guess which one is happening to you.

It covers every active ingredient that matters in medical-grade skincare, in the same format each time: what it does, the concentration that actually produces results, the pH it needs, who it suits, what it pairs with, what it fights with, when to apply it, and how long until you see change. Where Health Canada draws a line (hydroquinone, retinoids, acids), we say where that line is.

Use it two ways. Read an entry when a product label mentions an ingredient you don't know. Or start from the By concern section at the bottom, find your skin goal, and work back to the ingredients that solve it. Each entry links to a full deep-dive on this blog if you want the long version.

A note on "medical-grade". The ingredients here are the same ones in drugstore products. The difference is dose, stability and delivery. A drugstore vitamin C serum might contain 3% ascorbic acid at the wrong pH in a clear bottle; a medical-grade one contains 10–20% L-ascorbic acid at pH 2.5–3.5 in an airless, opaque container. Same ingredient, different outcome. What Is Medical-Grade Skincare? explains that gap in full; this guide tells you the numbers to look for, ingredient by ingredient.

Jump to: Quick reference · Antioxidants · Retinoids · Exfoliating acids · Pigment correctors · Barrier & hydration · Collagen & repair · Sun protection · Acne & oil control · Pairing matrix · Concentrations & Canadian limits · By concern · FAQ

How to read each entry

Every ingredient below uses the same eight fields so you can compare them directly.

Two rules that apply to every entry. First, patch-test a new active on the jawline for three nights before using it on the whole face. Second, no active works without daily broad-spectrum SPF; several (retinoids, acids, hydroquinone) actively work against you without it.

Quick reference: every active at a glance

If you only read one table, read this one. Concentrations are for leave-on products unless noted.

A. Antioxidants

Antioxidants neutralize the free radicals that UV, pollution and heat generate in skin. Sunscreen stops most UV; antioxidants clean up what gets through. Together they prevent more aging than either alone.

Vitamin C (L-ascorbic acid)

• Does: Donates electrons to neutralize free radicals; is a required cofactor for collagen synthesis; blocks tyrosinase, the enzyme that makes melanin. The only form proven to do all three.
• Effective %: 10–20%. Absorption plateaus at 20%; 15% is the sweet spot for most skin.
• pH: 3.5 or below, ideally 2.5–3.2. Above 3.5, L-ascorbic acid stays on the surface.
• Best for: Dullness, early photoaging, uneven tone, anyone over 25 as prevention. Sensitive or rosacea-prone skin usually tolerates derivatives better.
• Pair with: Vitamin E and ferulic acid (the classic triad doubles photoprotection); sunscreen on top.
• Avoid with: Retinol in the same step (pH mismatch), benzoyl peroxide (oxidizes it), copper peptides (chelation). Niacinamide is fine; the "they cancel out" claim came from 1960s research on unstabilized formulas.
• When: AM, on clean dry skin, before moisturizer and SPF. Can be used PM if you prefer.
• Results in: Brighter tone in 4 weeks; pigment and fine lines in 8–12.
• Storage: Opaque, airless, cool. If it turns orange-brown it has oxidized and will do nothing.
• Deep-dives: Best Vitamin C Serums in Canada · Vitamin C: The Complete Dermatologist Guide · Best SkinCeuticals C E Ferulic Alternatives

Vitamin C derivatives (THD ascorbate, MAP, SAP, ascorbyl glucoside)

• Does: Converts to ascorbic acid in skin. Oil-soluble THD (tetrahexyldecyl ascorbate) penetrates well and is the most stable; water-soluble MAP (magnesium ascorbyl phosphate) and SAP are gentler and work at neutral pH.
• Effective %: THD 10–30%; MAP/SAP 3–10%; ascorbyl glucoside 2–5%.
• pH: 5–7, so they coexist with almost anything.
• Best for: Sensitive, rosacea-prone, dry and reactive skin that stings with L-ascorbic acid. THD suits dry and mature skin; MAP suits oily and acne-prone skin.
• Avoid with: Nothing meaningful.
• When: AM or PM.
• Results in: 8–12 weeks; slower than L-AA, far better tolerated.

Vitamin E (tocopherol)

• Does: Lipid-phase antioxidant; protects cell membranes and recycles vitamin C. Weak alone, strong in combination.
• Effective %: 0.5–1%.
• Best for: Dry and mature skin; anyone using L-ascorbic acid.
• Avoid with: Nothing. Can be comedogenic for very acne-prone skin at high levels.

Ferulic acid

• Does: Plant antioxidant that stabilizes vitamins C and E and roughly doubles their photoprotection (the Duke University finding behind the C + E + ferulic formula).
• Effective %: 0.5–1%.
• Best for: Anyone using vitamin C.

Resveratrol, green tea (EGCG), coenzyme Q10

• Does: Secondary antioxidants with anti-inflammatory activity. Useful in PM antioxidant serums and as support, not as a primary treatment.
• Effective %: Resveratrol 0.5–1%; EGCG 1–3%; CoQ10 0.5–1%.
• When: PM pairs well with retinol since they calm inflammation.

B. Retinoids

Retinoids are vitamin A derivatives and the most-studied anti-aging ingredients in dermatology. They speed cell turnover, thicken the dermis, build collagen, shrink pore appearance and clear pigment. Every retinoid converts to retinoic acid in skin; the conversion steps determine strength and irritation.

Strength ladder (weakest to strongest): retinyl palmitate → retinol → retinaldehyde → adapalene / tretinoin / tazarotene (prescription).

Retinol

• Does: Converts to retinaldehyde, then retinoic acid, which binds nuclear receptors and changes gene expression: more collagen, faster turnover, less melanin transfer, smaller oil glands.
• Effective %: 0.25–1%. Start at 0.25–0.3%, move up every 8–12 weeks. Encapsulated retinol at 0.5% often outperforms plain retinol at 1% because it stays stable and releases slowly.
• pH: 5.5–6.5. This is why layering it with low-pH vitamin C or acids in the same step reduces both.
• Best for: Fine lines, texture, enlarged pores, acne, sun damage, dark spots. Anyone 25+ as prevention.
• Pair with: Niacinamide (cuts irritation), ceramide moisturizer, peptides, growth factors, hyaluronic acid.
• Avoid with: L-ascorbic acid, AHAs/BHA and benzoyl peroxide in the same step. All can be used in the same routine at different times (vitamin C AM, retinol PM; acids on alternate nights).
• When: PM only; UV degrades it. Start 2 nights per week, add a night every 2 weeks. Pea-sized amount. Buffer by applying moisturizer first if you react.
• Results in: Smoother texture at 8 weeks; pigment at 12; wrinkle depth at 6 months. Expect dryness and flaking in weeks 2–4 ("retinization"), which resolves.
• Not for: Pregnancy or breastfeeding.
• Deep-dives: Retinol Explained · SkinMedica Retinol Complex: Which Strength · How to Start Retinol Without Redness · Vitamin C vs Retinol

Retinaldehyde (retinal)

• Does: One conversion step from retinoic acid, so it works up to 11× faster than retinol at equal concentration, with similar tolerability. Also mildly antibacterial, useful for acne.
• Effective %: 0.05–0.1%.
• Best for: People who want faster results than retinol without a prescription.
• When / Avoid with / Not for: As retinol.

Retinyl esters (retinyl palmitate, retinyl propionate)

• Does: Three conversion steps away; mild. Found in "gentle" or eye-area products.
• Effective %: 0.5–2%, but potency is low regardless.
• Best for: Very sensitive skin, eyelids, first-ever retinoid. Not a substitute for retinol if you want wrinkle change.

Bakuchiol ("bio-retinol")

• Does: Plant extract that activates some of the same genes as retinol without binding retinoid receptors. Clinical data show comparable wrinkle and pigment improvement at 0.5–1% with less irritation.
• Effective %: 0.5–2%.
• Best for: Pregnancy, rosacea, retinol-intolerant skin. Can be used AM and PM; not photosensitizing.
• Deep-dive: Bio-Retinol vs Retinol

Tretinoin, adapalene, tazarotene (prescription)

• Does: Retinoic acid itself (tretinoin) or synthetic receptor-selective retinoids. No conversion needed. In Canada all three require a prescription.
• Effective %: Tretinoin 0.025–0.1%; adapalene 0.1–0.3%; tazarotene 0.05–0.1%.
• Best for: Moderate-to-severe acne, significant photoaging, when OTC retinol has plateaued.
• Note: Everything in this guide about pairing, timing and sun protection applies with more force to prescription retinoids. Talk to your dermatologist before adding acids or hydroquinone.

C. Exfoliating acids

Chemical exfoliants dissolve the bonds holding dead cells to the surface so they shed evenly. Done right, two or three times a week, they improve texture, tone and product penetration. Done daily at high strength, they thin the barrier and cause the exact redness and sensitivity people then try to treat.

Choosing by skin type: oily/acne → salicylic (BHA); normal/sun-damaged → glycolic; dry/sensitive → lactic or mandelic; reactive/rosacea → PHA or azelaic.

Glycolic acid (AHA)

• Does: Smallest AHA molecule, penetrates deepest. Loosens surface cells, stimulates collagen and hyaluronic acid production in the dermis, fades surface pigment.
• Effective %: 5–10% leave-on; 8–15% in rinse-off; 20–70% in professional peels only.
• pH: 3.5–4. The free-acid value (concentration × pH) determines strength, not the headline %.
• Best for: Texture, sun damage, fine lines, post-acne marks on normal to oily skin.
• Avoid with: Retinol, vitamin C and other acids in the same step. Rosacea, eczema, active barrier damage.
• When: PM, 2–3× per week, on alternate nights from retinol. Daily SPF is mandatory; AHAs increase sun sensitivity for a week after each use.
• Results in: Smoother texture in 2–4 weeks.

Lactic acid (AHA)

• Does: Larger molecule than glycolic, so it stays more superficial and irritates less. A natural moisturizing factor, so it hydrates while it exfoliates.
• Effective %: 5–10% leave-on.
• Best for: Dry, dehydrated, mature or mildly sensitive skin; first AHA.

Mandelic acid (AHA)

• Does: Largest AHA, oil-soluble, antibacterial. Penetrates slowly and evenly, so it rarely causes the post-inflammatory darkening that glycolic can trigger in deeper skin tones.
• Effective %: 5–10%.
• Best for: Darker skin, melasma-prone skin, sensitive acne-prone skin.

Salicylic acid (BHA)

• Does: Oil-soluble, so it travels into the pore and dissolves the sebum-and-dead-cell plug that causes blackheads and breakouts. Anti-inflammatory (it is chemically related to aspirin).
• Effective %: 0.5–2%. 2% is the Canadian cosmetic ceiling and all that is needed.
• pH: 3–4.
• Best for: Oily skin, blackheads, enlarged pores, acne, keratosis pilaris on the body.
• Avoid with: Retinol in the same step (fine on alternate nights or AM/PM). Aspirin allergy. Pregnancy at >2% or over large areas.
• When: AM or PM. As a cleanser it can be daily; as a leave-on, 3× per week to start.
• Results in: Fewer blackheads in 2 weeks; acne in 4–6.
• Deep-dives: Best Face Exfoliants in Canada · Retinol vs Salicylic Acid · Salicylic Acid Mistakes Everyone Makes

Polyhydroxy acids (gluconolactone, lactobionic acid)

• Does: Very large molecules; exfoliate the outermost layer only, attract water, and act as antioxidants. The gentlest chemical exfoliant.
• Effective %: 5–10%.
• Best for: Rosacea, eczema-prone, post-procedure and retinoid-sensitive skin. Safe in pregnancy.
• When: Either, up to daily.

Azelaic acid

• Does: A dicarboxylic acid, not a true exfoliant. Kills acne bacteria, calms inflammation, normalizes cell shedding inside the pore, and inhibits tyrosinase in overactive pigment cells only, which makes it uniquely useful for post-inflammatory marks and melasma.
• Effective %: 10% cosmetic; 15% gel and 20% cream are prescription in Canada.
• Best for: Rosacea, acne, post-acne marks, melasma, pregnancy (the first-line pregnancy-safe treatment for both acne and pigment).
• Avoid with: Nothing meaningful; it layers with retinol, niacinamide and vitamin C.
• When: Either, once or twice daily. Mild itch or tingling in week one is normal.
• Results in: Redness in 4 weeks; acne and pigment in 8–12.
• Deep-dive: Azelaic Acid: The Underrated Hero

D. Pigment correctors

Dark spots form when melanocytes overproduce melanin and hand it to surrounding cells. Correctors work at one of three points: slow the enzyme that makes melanin (tyrosinase inhibitors), stop the hand-off (niacinamide), or speed removal of pigmented cells (retinoids and acids). Combining one from each group outperforms any single ingredient, and nothing holds without daily iron-oxide SPF.

Know your pigment type first: sun spots, melasma and post-inflammatory marks respond to different protocols. Hyperpigmentation Types Explained covers the diagnosis.

Hydroquinone

• Does: The strongest topical tyrosinase inhibitor; also reduces melanosome formation. Gold standard for melasma and stubborn sun spots for 50 years.
• Effective %: 2% is available over the counter in Canada (Health Canada permits up to 2% in cosmetics and natural health products; US-based websites and AI tools often claim otherwise). 4% requires a prescription.
• Best for: Melasma, sun spots, post-inflammatory marks that have not responded to gentler agents.
• Pair with: Vitamin C (stabilizes it and adds brightening), retinol on alternate nights, tranexamic acid, SPF with iron oxides.
• Avoid with: Benzoyl peroxide (temporary staining), resorcinol-containing products. Do not use continuously beyond 12 weeks; cycle 3 months on, 3 months off, to avoid the rare paradoxical darkening (ochronosis).
• When: PM, thin layer on affected areas only.
• Results in: Lightening at 4–6 weeks; near-full fade at 12.
• Not for: Pregnancy, breastfeeding.
• Deep-dives: Is Hydroquinone Available OTC in Canada? · Vivier Advanced Skin Lightening Serum Review · Best Dark Spot Correctors in Canada

Tranexamic acid

• Does: Blocks the plasmin pathway that UV uses to switch on melanocytes. The only corrector that targets the vascular and inflammatory trigger of melasma, not just the enzyme.
• Effective %: 2–5% topical.
• Best for: Melasma, especially hormonal or heat-triggered; pigment that returns every summer.
• Pair with: Hydroquinone, niacinamide, vitamin C, kojic acid. Safe to use year-round, so it holds results during hydroquinone's off-cycle.
• Avoid with: Nothing topical. Oral tranexamic acid is prescription-only and has clotting contraindications.
• When: Either, twice daily.
• Results in: 8–12 weeks.

Kojic acid

• Does: Fungal-derived tyrosinase inhibitor that chelates the copper the enzyme needs.
• Effective %: 1–2%. Unstable; look for kojic dipalmitate in daytime products.
• Best for: Sun spots and uneven tone; often paired with hydroquinone in corrector formulas.
• Avoid with: Can sensitize; patch-test.

Arbutin (alpha-arbutin)

• Does: Glycoside of hydroquinone that releases it slowly in skin. Gentler, slower, no cycling needed.
• Effective %: 1–2%.
• Best for: Maintenance between hydroquinone cycles; mild, diffuse unevenness; sensitive skin.

Licorice root (glabridin), vitamin C, niacinamide, retinoids, azelaic acid

Each appears elsewhere in this guide and is a legitimate pigment agent. In practice a medical-grade corrector routine looks like: AM vitamin C + niacinamide + tinted mineral SPF; PM hydroquinone or tranexamic acid, alternating nights with retinol. Skin Care Routine for Dark Spots lays it out step by step; How to Prevent and Treat Pigmentation This Summer covers the seasonal version.

E. Barrier and hydration

The skin barrier is a brick wall: corneocytes are the bricks, and a mortar of ceramides, cholesterol and fatty acids holds them in place and keeps water in. Every active in this guide works better on an intact barrier, and most irritation complaints are barrier damage, not ingredient allergy. In a Canadian winter, this section matters more than any other.

Ceramides

• Does: Make up roughly half the barrier's lipid mortar. Topical ceramides replace what cleansing, actives, cold air and age strip out, and measurably reduce water loss within days.
• Effective %: Formulas rarely list a percentage. Look for ceramides NP, AP, EOP (ceramides 3, 6-II, 1) alongside cholesterol and fatty acids in roughly a 3:1:1 ratio; the ratio matters more than the total.
• Best for: Dry, sensitive, eczema-prone, retinoid-irritated and post-procedure skin. Everyone in winter.
• Pair with: Everything. Apply after actives to seal them in, or before as a buffer.
• When: Either, daily.
• Results in: Less tightness in days; visibly calmer skin in 2–4 weeks.
• Deep-dives: Best Skin Barrier Repair Creams · Best Ceramide Products in Canada for Winter · How to Repair Skin Barrier After Acne

Hyaluronic acid (and sodium hyaluronate)

• Does: Humectant that binds up to 1,000× its weight in water. High-molecular-weight HA sits on the surface and plumps; low-molecular-weight HA penetrates and hydrates deeper layers. Multi-weight formulas do both.
• Effective %: 0.1–2%. More is not better; above 2% it can pull water out of skin in dry air.
• Best for: Every skin type; dehydrated oily skin in particular.
• Avoid with: Nothing. In dry Canadian winters, always seal it with a moisturizer or it evaporates and takes water with it.
• When: Either, on damp skin, before moisturizer.
• Results in: Immediate plumping; cumulative over weeks.

Niacinamide (vitamin B3)

• Does: The most versatile ingredient in skincare. Boosts ceramide production, reduces water loss, regulates sebum, shrinks pore appearance, blocks melanin transfer to surface cells, calms redness, and reduces the inflammation retinoids cause.
• Effective %: 2–5% does all of the above. 10% adds little and can flush sensitive skin.
• pH: 5–7; coexists with everything.
• Best for: Oily, acne-prone, rosacea, pigmented, retinoid-using and ageing skin. In practice: everyone.
• Pair with: Retinol (halves irritation), vitamin C (the conflict is a myth), acids, hydroquinone, SPF.
• Avoid with: Nothing meaningful.
• When: Either, daily.
• Results in: Oil and redness in 2–4 weeks; pores and pigment in 8.
• Deep-dives: Niacinamide Serums in Canada · Why Niacinamide Belongs in Every Routine

Glycerin

• Does: The most proven humectant in dermatology; draws water into the stratum corneum and improves barrier recovery.
• Effective %: 3–10%. Often in the top five ingredients of a good moisturizer.
• Best for: All skin types. Underrated because it is cheap.

Squalane

• Does: Hydrogenated squalene, a lipid skin makes naturally. Lightweight, non-comedogenic emollient that softens and reduces water loss without feeling heavy.
• Effective %: 5% in a moisturizer to 100% as a facial oil.
• Best for: All types, including oily and acne-prone.

Cholesterol and fatty acids (linoleic acid, stearic acid)

• Does: The other two-fifths of the barrier mortar. Linoleic acid deficiency in sebum is linked to acne; replacing it topically helps comedones.
• Best for: Barrier repair formulas with ceramides; acne-prone dry skin.

Panthenol (pro-vitamin B5)

• Does: Converts to pantothenic acid, speeds wound healing, reduces itch and redness, adds humectancy.
• Effective %: 1–5%.
• Best for: Post-procedure, post-retinoid irritation, windburn, sensitive skin.

Occlusives (petrolatum, dimethicone, shea butter)

• Does: Form a film that physically blocks water loss. Petrolatum reduces it by about 98%, more than anything else.
• Best for: The last step on very dry or compromised skin, and as "slugging" over a bland moisturizer in deep winter. Not for acne-prone skin on the full face.
• Deep-dives: Best Medical-Grade Moisturizers in Canada · Best Skincare for Canadian Winters

F. Collagen and repair

After 25, collagen declines about 1% a year, and faster through perimenopause. Retinoids force new collagen by stressing skin into repair mode. Growth factors and peptides do it by sending the signal directly, without the irritation. They are the ingredients to add when retinol alone has plateaued, or when skin cannot tolerate it.

Growth factors

• Does: Naturally occurring proteins (EGF, TGF-β, FGF, PDGF and others) that tell fibroblasts to produce collagen, elastin and hyaluronic acid, and that coordinate wound healing. Medical-grade formulas use either human fibroblast-derived mixtures (SkinMedica TNS) or plant-derived and biosynthetic equivalents.
• Effective %: Not expressed as a percentage; potency depends on the source, the number of factors, and stabilization. Human-derived, multi-factor blends have the most clinical data.
• Best for: Fine lines, loss of firmness, crepey texture, dullness, post-procedure healing, skin over 35. Suitable for sensitive and rosacea-prone skin because they cause no irritation.
• Pair with: Retinol (they repair what retinol stimulates), vitamin C, peptides, SPF. Apply growth factors first, on clean skin, before heavier products.
• Avoid with: Nothing. Prudence suggests avoiding them on active skin cancers or during pregnancy for lack of data, not because of known harm.
• When: Either, daily. Most protocols use them AM and PM.
• Results in: Texture and radiance at 4–8 weeks; firmness and wrinkle depth at 12–24.
• Deep-dive: Growth Factors in Skincare: The Complete Dermatologist Guide

Signal peptides (palmitoyl pentapeptide-4 / Matrixyl, palmitoyl tripeptide-1, tripeptide-5)

• Does: Short amino-acid chains that mimic the fragments collagen leaves behind when it breaks down, which tricks fibroblasts into producing more.
• Effective %: Formulas list the peptide complex, typically 2–10%. Look for peptides in the first half of the ingredient list.
• Best for: Early-to-moderate lines, prevention in the 30s, anyone retinol-intolerant.
• Pair with: Niacinamide, hyaluronic acid, growth factors, retinol (alternate or layer; no conflict).
• Avoid with: Low-pH acids and L-ascorbic acid in the same step, which can break the peptide bonds. Use at different times.
• When: Either.
• Results in: 8–12 weeks.

Carrier peptides (copper tripeptide-1, GHK-Cu)

• Does: Deliver copper, a cofactor for the enzymes that cross-link collagen and elastin and for wound healing. Also anti-inflammatory and antioxidant.
• Effective %: 0.5–2%.
• Best for: Firmness, post-procedure healing, mature skin.
• Avoid with: L-ascorbic acid (copper and ascorbic acid react), strong acids. Use copper peptides PM, vitamin C AM.

Neurotransmitter-inhibiting peptides (acetyl hexapeptide-8 / Argireline, pentapeptide-18)

• Does: Reduce the muscle-contraction signal at the skin surface. A modest, temporary softening of expression lines, not a Botox replacement.
• Effective %: 5–10%.
• Best for: Forehead and crow's-feet lines; people avoiding injectables.
• Results in: 2–4 weeks; results fade when stopped.

Polyamine-DAB and other proprietary repair complexes

• Does: Vivier's Polyamine-DAB (diaminobutane) is a growth-factor-like molecule shown to stimulate fibroblast activity; it anchors their GrenzCine line and Crème 47. Other brands have their own proprietary complexes (SkinMedica's TNS-MR, PCA's ExLinea peptide blend). Evaluate these on the brand's published clinical data, not the ingredient name.
• Deep-dives: Peptide Serums in Canada · Vivier Crème 47 Review · What Really Causes Skin to Age

G. Sun protection

UV causes roughly 80% of visible facial aging and every form of hyperpigmentation worsens under it. Sunscreen is the only product in this guide that works on day one and the only one every other ingredient depends on. Canadian winters do not exempt you: UVA passes through cloud and glass and reflects off snow at up to 80%.

Reading the label. SPF measures UVB (burning) only. For UVA (aging, pigment) look for "broad spectrum" plus a PA rating (PA+++ or PA++++) or the UVA-in-circle logo. Reapply every 2 hours outdoors; the SPF 30-vs-50 difference matters less than the amount (a quarter-teaspoon for the face) and the reapplication. UVA vs UVB explains the physics.

Zinc oxide

• Does: Mineral filter that reflects and absorbs across the full UVB and UVA spectrum, including long UVA1. The only single ingredient that is broad-spectrum on its own. Anti-inflammatory; sits on top of skin rather than absorbing into it.
• Effective %: 10–25%. Below 10%, UVA coverage drops. Micronized (non-nano or nano) versions reduce white cast.
• Best for: Sensitive, rosacea, melasma, acne-prone, post-procedure, pregnancy, children. The default recommendation in medical-grade skincare.
• Avoid with: Nothing. Can pill over silicone-heavy serums; let serums dry first.
• When: AM, last skincare step, before makeup.

Titanium dioxide

• Does: Mineral filter strong in UVB and short UVA; weaker against long UVA, so it is usually paired with zinc oxide.
• Effective %: 5–15%.
• Best for: Paired formulas; very fair skin. Leaves more white cast than zinc.

Iron oxides

• Does: The pigments that tint mineral sunscreens. They block visible light (blue light and HEV) which triggers melasma in darker skin types and which no UV filter stops.
• Effective %: 3% or more produces meaningful visible-light protection; most tinted medical-grade SPFs qualify.
• Best for: Melasma, post-inflammatory pigment, Fitzpatrick III–VI skin, anyone using hydroquinone or tranexamic acid. For these people a tinted sunscreen is a treatment, not a cosmetic choice.
• Deep-dives: Best Tinted Sunscreen for Face · Where to Buy Colorescience in Canada

Chemical (organic) filters: avobenzone, octocrylene, homosalate, octisalate, oxybenzone, Tinosorb S/M, Mexoryl SX/XL

• Does: Absorb UV and convert it to heat. Lighter, more cosmetically elegant, easier to formulate at high SPF. Avobenzone covers UVA but degrades in light unless stabilized (by octocrylene, or in the newer Tinosorb and Mexoryl filters, which are stable and broad-spectrum and approved in Canada).
• Best for: Oily skin and darker tones wanting no cast; sport and water use.
• Avoid with: Rosacea and eczema (heat conversion can flush), post-procedure skin, infants. Oxybenzone is the filter most associated with sensitization; it is increasingly dropped from medical-grade lines.
• When: AM, last step, 15 minutes before exposure.

Antioxidants in sunscreen

Vitamin C or E, niacinamide and green tea in a sunscreen extend protection by mopping up the radicals filters miss. A vitamin C serum under SPF is the gold-standard morning pairing.

Deep-dives: Best Medical-Grade Sunscreens in Canada · Best Sunscreens for Acne-Prone Skin · EltaMD Is Back in Canada

H. Acne and oil control

Acne has four drivers: excess sebum, abnormal shedding inside the pore, C. acnes bacteria, and inflammation. Each ingredient here targets one or two. Effective routines hit at least three, which is why a single "acne product" rarely works alone. Salicylic acid, azelaic acid, niacinamide and retinoids all belong to this section too; see their entries above.

Benzoyl peroxide

• Does: Releases oxygen inside the pore, killing C. acnes on contact. Bacteria cannot develop resistance to it, unlike to antibiotics. Mildly keratolytic.
• Effective %: 2.5–5%. Studies show 2.5% is as effective as 10% with a fraction of the irritation. Available over the counter in Canada up to 10%.
• Best for: Inflamed, red, pustular acne; adult hormonal breakouts along the jaw. Not for blackheads (use salicylic).
• Pair with: Niacinamide, ceramide moisturizer, adapalene (the standard dermatology combination).
• Avoid with: Retinol and L-ascorbic acid in the same step (it oxidizes both); hydroquinone (temporary staining). It bleaches towels and pillowcases.
• When: As a wash, daily. As a leave-on, PM spot treatment or thin full-face layer; start every other day.
• Results in: 2–4 weeks.
• Deep-dives: Salicylic Acid vs Benzoyl Peroxide · Best Medicated Face Wash for Acne in Canada

Sulfur

• Does: Antibacterial and keratolytic; absorbs oil. Older than benzoyl peroxide and gentler, with a distinctive smell.
• Effective %: 3–10% in masks and spot treatments.
• Best for: Sensitive acne-prone skin, rosacea with papules, fungal (malassezia) folliculitis where salicylic and benzoyl fail.
• When: PM, as a mask 2–3× per week or overnight spot treatment.

Zinc (zinc PCA, zinc gluconate)

• Does: Reduces sebum output and inflammation; mildly antibacterial. Works in the background rather than as a lead treatment.
• Effective %: 0.1–1% topical.
• Best for: Oily skin, as a supporting ingredient in serums and moisturizers.

Clay (kaolin, bentonite) and charcoal

• Does: Absorb surface oil physically. Short-term mattifying; no effect on the causes of acne.
• Best for: Weekly masks on oily skin. Do not use more than twice a week or they strip the barrier and trigger rebound oil.

Tea tree oil

• Does: Antibacterial and anti-inflammatory; 5% gel performed comparably to 5% benzoyl peroxide in one trial, more slowly.
• Effective %: 5% diluted. Never neat.
• Avoid with: Sensitive skin; it is a common contact allergen.

Putting it together. An oily or acne-prone medical-grade routine usually reads: AM salicylic cleanser → niacinamide → oil-free SPF; PM gentle cleanser → retinoid (or azelaic acid) → benzoyl peroxide on active spots → lightweight ceramide moisturizer. Full routines by skin type: Best Acne Routine for Oily vs Dry Skin · Hormonal Acne Treatment in Canada · Acne vs Rosacea

Ingredient pairing matrix

Almost every ingredient in this guide can share a routine. The question is whether they can share a step. Read down the left column, across to the ingredient you want to add. Y = same step is fine. T = same routine, different time (AM/PM or alternate nights). N = keep apart.

The three real conflicts. Benzoyl peroxide oxidizes vitamin C and retinol and stains with hydroquinone. L-ascorbic acid chelates copper peptides. Low-pH acids and L-ascorbic acid in the same step as retinol reduce retinol's conversion. Everything else that gets labelled "don't mix" is a tolerance question, not a chemistry one.

The order within a step. Thinnest to thickest: water-based serums → treatment creams → moisturizer → SPF (AM) or occlusive (PM). Retinol goes on dry skin; hyaluronic acid goes on damp skin. Wait 60 seconds between layers; waiting longer adds nothing.

A standard medical-grade week:

Pigment correctors (hydroquinone, tranexamic acid, azelaic acid) slot into PM on retinol nights, applied first, thinly, to affected areas. Full routines: The Complete Skincare Layering Guide · Which Skincare Ingredients Can You Mix? · Morning vs Evening Skincare

Concentrations that matter, and where Canada draws the line

A label can say "with retinol" at 0.01% or "vitamin C" at 1%. Neither will change your skin. This table gives the threshold where each ingredient starts to work, the range medical-grade brands use, and the regulatory ceiling in Canada where one exists. Canadian limits come from Health Canada's Cosmetic Ingredient Hotlist and the Natural and Non-prescription Health Products Directorate; where a figure is a general industry guideline rather than a published limit, it is marked as such.

What "medical-grade" means in practice. Brands like Vivier, SkinMedica, PCA Skin, EltaMD and Colorescience formulate at the top of the effective range, stabilize the ingredient (airless packaging, encapsulation, pH control), and publish or sponsor clinical trials on the finished product rather than on the raw ingredient. That is the difference you pay for. Medical-Grade vs Drugstore Skincare goes through the economics.

Why Canada differs from the US. Several ingredients are regulated differently on each side of the border: 2% hydroquinone is OTC in Canada but was pulled from US OTC shelves in 2020; retinaldehyde and certain UV filters (Tinosorb, Mexoryl) are approved in Canada and not in the US; some US-market products are not licensed for sale here. US-based advice, and AI answers trained on it, frequently gets Canadian availability wrong.

By concern: which ingredients to reach for

Start with your goal, pick one ingredient from each column, and you have a routine. The "first" column is where to begin if you are adding one thing; "then" is what to layer in after 8 weeks; "support" never conflicts and can be added any time.

Not sure which concern is actually yours? The Baumann Skin Type Quiz sorts skin into 16 types in five minutes, and each type maps onto this table.

Frequently asked questions

What is the single most effective skincare ingredient?

Sunscreen, because it prevents the damage every other ingredient is treating. After that, retinol has the most evidence for aging and acne, and L-ascorbic acid for brightening and antioxidant protection.

Can I use vitamin C and niacinamide together?

Yes. The claim that they cancel each other out comes from 1960s research on unstabilized ascorbic acid at high heat. Modern formulas combine them, and studies show additive brightening.

Can I use retinol and vitamin C together?

In the same routine, yes: vitamin C in the morning, retinol at night. In the same step, no: L-ascorbic acid needs pH below 3.5 and retinol works at 5.5–6.5, so layering them reduces both.

Is hydroquinone legal in Canada?

Yes. Up to 2% is available over the counter from authorized retailers; 4% requires a prescription. Use it in 12-week cycles with a break between.

What percentage of retinol should I start with?

0.25–0.3%, two nights a week, increasing frequency every two weeks. Move to 0.5% after 8–12 weeks if tolerated, and to 1% only if you want more and your skin is settled.

How long before an ingredient works?

Hydration ingredients work immediately. Exfoliants show in 2–4 weeks. Vitamin C, niacinamide and azelaic acid take 4–8 weeks. Retinol, hydroquinone, peptides and growth factors take 8–12 weeks, and up to 6 months for wrinkle depth and firmness. Skin turns over every 28–40 days, and most actives need two to three cycles.

Which ingredients are safe in pregnancy?

Azelaic acid, niacinamide, vitamin C, hyaluronic acid, ceramides, glycolic and lactic acid at cosmetic strengths, bakuchiol and mineral sunscreen. Avoid all retinoids, hydroquinone, salicylic acid above 2% or over large areas, and oral tranexamic acid.

Does a higher percentage always mean a better product?

No. Every active has a ceiling where irritation rises faster than benefit: 20% for L-ascorbic acid, 1% for retinol, 10% for glycolic acid, 5% for niacinamide and benzoyl peroxide. Stability, pH and packaging decide whether a product at a sensible percentage actually delivers.

What is the difference between medical-grade and drugstore versions of the same ingredient?

Concentration at the effective level, stabilization so the ingredient is still active when it reaches your skin, pH control, and clinical testing on the finished product. The molecule is the same; the formula is not.

Can I use everything in this guide at once?

No. A complete routine needs an antioxidant, a retinoid or alternative, a barrier moisturizer and SPF. Add a pigment corrector or an exfoliant only if you have that concern. More than two new actives at a time is how most people end up with a damaged barrier.

How to use this guide

Bookmark it. When a product label lists something you don't recognize, look it up here. When a routine isn't working, check three things against the entries: is the concentration in the effective range, is the pH right, and are you layering two things that belong in different steps.

If you would rather not do the matching yourself, Axon, Skin Boutique Online's AI skincare assistant, uses this same ingredient logic to build an AM/PM routine for your skin type and concerns in a few minutes, and answers any ingredient question around the clock. Every product it recommends is an authentic, Canadian-stocked medical-grade formula from Vivier, SkinMedica, PCA Skin, Colorescience or EltaMD.

This encyclopedia is reviewed and updated twice a year as new ingredients, concentrations and Health Canada rulings appear. Last updated October 2026.

This guide is educational and is not a substitute for medical advice. See a dermatologist for persistent or severe skin conditions, before starting prescription-strength ingredients, and during pregnancy.