The Skincare Ingredient Glossary: A Plain-English Reference

Hyaluronic Acid

A humectant — a moisture-attracting molecule — that draws water into the skin's outer layers. It occurs naturally in the body and is well tolerated by most skin types, including sensitive. Found in serums, moisturizers, and toners.

Niacinamide

A form of vitamin B3 that helps support the skin barrier, even out skin tone, and minimize the appearance of pores. It's generally gentle enough for daily use and plays well with most other ingredients.

AHA (Alpha Hydroxy Acid)

A class of water-soluble exfoliating acids — including glycolic and lactic acid — that work on the skin's surface to loosen dead cells and promote a smoother, more even texture. Most effective for dry or sun-damaged skin.

BHA (Beta Hydroxy Acid)

An oil-soluble exfoliating acid, most commonly salicylic acid, that can penetrate into pores to clear out excess sebum and debris. Particularly useful for oily or acne-prone skin.

Retinol / Retinoid

Vitamin A derivatives that support cell turnover and collagen production. Retinoids (the prescription category) are stronger; retinol is the over-the-counter form. Both can cause initial dryness or flaking and require gradual introduction.

Vitamin C (L-Ascorbic Acid)

An antioxidant that helps brighten skin tone and protect against environmental stressors like UV exposure and pollution. Most potent in its pure L-ascorbic acid form, though less stable than derivatives like ascorbyl glucoside.

Ceramide

Lipids (fats) that occur naturally in the skin and form a key part of the skin barrier. Ceramide-containing moisturizers help reinforce this barrier, making them especially helpful for dry or compromised skin.

Peptide

Short chains of amino acids that serve as building blocks for proteins like collagen and elastin. In skincare, peptides are used to support firmness and skin structure, though evidence strength varies by specific peptide.

SPF (Sun Protection Factor)

A measure of how well a sunscreen protects against UVB rays, the type most associated with sunburn and skin damage. Dermatologists broadly recommend SPF 30 or higher for daily use, rain or shine.

Occlusives

Thick, film-forming ingredients — such as petrolatum, beeswax, or shea butter — that create a physical barrier on the skin's surface to lock in moisture. Often found in the final step of a routine, like a night cream or balm.

Emollient

Ingredients that soften and smooth the skin by filling gaps between skin cells. Common emollients include plant oils, squalane, and fatty alcohols. They sit between lightweight humectants and heavy occlusives in terms of texture.

Exfoliant

Any ingredient or physical agent that removes dead skin cells from the skin's surface. Chemical exfoliants (AHAs, BHAs, PHAs) use acids; physical exfoliants use particles or tools. Over-exfoliating can disrupt the skin barrier.