Skincare Ingredients Glossary: A Plain-Language Reference

Retinol

A vitamin A derivative that encourages skin cell turnover and stimulates collagen production. It's widely studied for its role in reducing the appearance of fine lines and uneven texture, though it can cause dryness and sensitivity when introduced too quickly.

Niacinamide

Also called vitamin B3, niacinamide is a water-soluble ingredient that supports the skin barrier, helps regulate oil production, and may reduce the appearance of pores and uneven skin tone. It is generally considered well-tolerated across skin types.

Hyaluronic Acid

A humectant — meaning it draws moisture from the environment into the skin — that occurs naturally in the body. In skincare, it helps skin feel plumper and more hydrated without adding oil or heaviness.

AHA (Alpha Hydroxy Acid)

A class of water-soluble acids, including glycolic and lactic acid, that exfoliate the surface layer of skin by loosening the bonds between dead cells. AHAs are often used to improve texture, brightness, and tone.

BHA (Beta Hydroxy Acid)

A class of oil-soluble acids, most commonly salicylic acid, that can penetrate into pores to dissolve excess sebum and dead skin buildup. BHAs are frequently recommended for acne-prone or oily skin types.

Ceramides

Lipid molecules naturally found in the outermost layer of skin that help maintain the skin barrier — the protective seal that keeps moisture in and irritants out. Ceramide-containing products are often recommended for dry or compromised skin.

Vitamin C (L-Ascorbic Acid)

An antioxidant that helps neutralize free radicals, supports collagen synthesis, and is commonly used to brighten skin and reduce the appearance of dark spots. It can be unstable in formulations and may cause irritation for sensitive skin at high concentrations.

SPF (Sun Protection Factor)

A measure of how well a sunscreen product protects skin from UVB rays, which contribute to sunburn and skin damage. SPF is not a measure of time in the sun but of the relative level of protection compared to no sunscreen.

Peptides

Short chains of amino acids that act as messengers in the skin, signaling it to produce more collagen or elastin. In topical skincare, peptides are associated with firming and anti-aging effects, though research on their efficacy varies by formulation.

Humectant

An ingredient category that attracts water to the skin. Common humectants in skincare include hyaluronic acid, glycerin, and aloe vera. They work best when applied to damp skin and sealed in with a moisturizer.

Emollient

An ingredient that softens and smooths the skin by filling in gaps between skin cells. Oils, butters, and fatty alcohols are common emollients found in moisturizers and balms.

Occlusives

Ingredients that form a physical barrier on the skin's surface to prevent water loss. Petrolatum, beeswax, and dimethicone are widely used occlusives, often found in thick creams and ointments.