Skincare Ingredients Glossary A–Z

Best for: Dull skin, texture, hyperpigmentation

Water-soluble chemical exfoliants that work on the skin's surface to dissolve dead cell bonds, revealing smoother, brighter skin underneath. Glycolic acid is the strongest and most studied; lactic acid is gentler and adds hydration; mandelic acid is best for sensitive and darker skin tones (less risk of post-inflammatory hyperpigmentation). Use 2–3 times per week at night. Start with low concentrations (5–8%) and build up.

Best for: Acne, rosacea, hyperpigmentation

A multitasking acid produced naturally by yeast on your skin. Azelaic acid reduces acne-causing bacteria, calms redness (making it one of the few acids safe for rosacea), and fades dark spots by inhibiting tyrosinase (the enzyme that produces melanin). Available in 10% over-the-counter and 15–20% prescription strengths. Can be used morning or night.

Best for: Oily skin, acne, blackheads, clogged pores

Oil-soluble chemical exfoliant that penetrates into pores to dissolve sebum plugs and clear congestion from inside. This makes BHA the gold standard for acne-prone and oily skin. Also has anti-inflammatory properties that reduce redness around breakouts. Typical concentrations: 0.5–2%. Use 2–3 times per week.

Best for: All skin types, especially dry and sensitive

Lipids (fats) that naturally make up ~50% of your skin barrier. They act like mortar between skin cells, holding the barrier together and preventing moisture loss. Topical ceramides are essential for anyone with a compromised barrier — dry skin, eczema, or anyone using retinol or chemical exfoliants (which can thin the barrier). Found in moisturizers and barrier-repair serums.

Best for: Sensitive skin, redness, wound healing

An herb used in traditional medicine for centuries, now backed by modern research for its wound-healing and anti-inflammatory properties. The active compounds (madecassoside, asiaticoside) promote collagen synthesis and calm irritation. Centella is one of the few actives unanimously recommended for sensitive and rosacea-prone skin.

Best for: All skin types

A humectant that draws water from the air and deeper skin layers into the epidermis. Glycerin is one of the most effective and well-tolerated hydrating ingredients available. It's found in nearly every moisturizer and cleanser on the market. Non-irritating, fragrance-free, and suitable for every skin type including sensitive.

Best for: Dehydrated skin, all skin types

A naturally occurring molecule in your skin that holds up to 1,000 times its weight in water. Topical hyaluronic acid acts as a powerful humectant, pulling moisture into the skin and plumping fine lines temporarily. Works best when applied to damp skin and sealed with a moisturizer. Look for multi-molecular weight formulations (low + high molecular weight) for both surface and deeper hydration.

Best for: All skin types — the universal ingredient

Niacinamide is the closest thing skincare has to a universal ingredient. At 2–5% concentrations, it strengthens the skin barrier, reduces redness, and improves hydration. At 5–10%, it regulates sebum production (great for oily skin), minimizes pore appearance, and fades hyperpigmentation. It's stable, well-tolerated, pairs with almost everything, and works morning or night. If you could only use one active ingredient, this would be the safest choice.

Best for: Anti-aging, firmness

Short chains of amino acids that act as cellular messengers, signaling your skin to produce more collagen, elastin, or other structural proteins. Different peptides have different functions: copper peptides promote wound healing, matrixyl stimulates collagen, and argireline has a mild botox-like effect on expression lines. Peptides are gentle, making them a good anti-aging option for people who can't tolerate retinol.

Best for: Anti-aging, acne, texture, hyperpigmentation

The most evidence-backed anti-aging ingredient available without a prescription. Retinol accelerates cell turnover, stimulates collagen production, smooths fine lines, and fades dark spots. Start low (0.25–0.3%), use 2–3 nights per week, and build tolerance over 2–3 months before increasing concentration. Causes initial purging and sun sensitivity — always use SPF. Do not combine with Vitamin C (use them at different times of day) or AHA/BHA on the same night.

Best for: Dry skin, all skin types

A lightweight, non-comedogenic oil derived from olives (or sugarcane). Squalane mimics your skin's natural sebum, making it one of the most easily absorbed face oils. It provides emollient moisture without greasiness, making it suitable even for oily skin types. Often used as the last step before SPF or as a moisturizer booster.

Best for: Everyone — non-negotiable

The single most important skincare ingredient. UV filters protect against UVA (aging) and UVB (burning) radiation. Mineral filters (zinc oxide, titanium dioxide) sit on top of the skin and reflect UV rays. Chemical filters (avobenzone, homosalate, octinoxate) absorb UV energy and convert it to heat. Both types are effective. Use SPF 30 minimum, SPF 50 recommended, applied generously and reapplied every 2 hours outdoors.

Best for: Brightening, antioxidant protection, anti-aging

A potent antioxidant that neutralizes free radicals generated by UV exposure and pollution. Regular use brightens skin tone, fades hyperpigmentation, and boosts collagen synthesis. L-ascorbic acid (10–20%) is the gold standard but is unstable and can irritate sensitive skin. Ascorbyl glucoside and magnesium ascorbyl phosphate are gentler, more stable alternatives. Use in the morning before SPF for maximum antioxidant synergy.

Best for: Dry skin, anti-aging, wound healing

An antioxidant that works synergistically with Vitamin C — when combined, they provide 4x more UV protection than either alone. Vitamin E is also an emollient that softens and conditions skin. Found in many moisturizers and sunscreens as a supporting ingredient.