Hyaluronic Acid, Niacinamide, AHAs, BHAs: A Plain-Language Glossary of Common Skincare Ingredients

How to Use This Glossary

Skincare labels are dense with chemical names, acronyms, and marketing language that can make even a simple moisturizer feel intimidating. This plain-language glossary cuts through that noise by defining the active ingredients you are most likely to encounter — what each one does, how it works, and which skin concerns it is typically used to address.

Each entry below reflects general, publicly established dermatological knowledge. Ingredient behavior can vary depending on a product's formulation, concentration, and pH — so understanding an ingredient's function is the first step, not a substitute for patch-testing or professional guidance. For a broader look at how products themselves are structured, see how to read a skincare label.

Hydration Ingredients: Hyaluronic Acid, Glycerin, and Ceramides

Hyaluronic acid (HA) is one of the most widely used hydrating ingredients in skincare. As a humectant, it draws water toward the skin's surface, which can temporarily improve the appearance of plumpness and fine lines. HA occurs naturally in the body's connective tissue and joints, and topical versions vary in molecular weight — smaller molecules may penetrate more deeply, while larger ones work primarily at the surface.

Glycerin is another common humectant, often paired with HA in serums and moisturizers. It is highly effective at retaining moisture and is generally non-irritating, making it suitable for sensitive skin types.

Ceramides serve a different but complementary function. Rather than pulling water in, ceramides help seal moisture within the skin by reinforcing the natural lipid barrier — the protective outer layer that prevents water loss and shields against environmental stressors. Many dermatologists recommend ceramide-containing products for dry, compromised, or eczema-prone skin.

If you are starting a skincare routine from scratch, hydrating ingredients like these are typically among the safest and most universally beneficial starting points.

Multi-Tasking Actives: Niacinamide, Vitamin C, and Peptides

Niacinamide (vitamin B3) has become one of the most recommended multi-functional ingredients in mainstream skincare. Research supports its role in reducing the appearance of enlarged pores, improving uneven skin tone, and strengthening the epidermal barrier. It also has a comparatively gentle profile, making it compatible with most other actives at appropriate concentrations.

Vitamin C (most commonly as L-ascorbic acid) functions as an antioxidant, helping to neutralize free radical damage caused by UV exposure and environmental pollution. It is frequently used to address hyperpigmentation and support the skin's collagen network. One important caveat: vitamin C is notoriously unstable — it degrades with exposure to light, air, and heat — so formulation quality and packaging matter significantly.

Peptides are shorter chains of amino acids used in many anti-aging formulations. The premise is that certain peptide sequences can signal the skin to produce more collagen, though the overall evidence base is considered more preliminary than that for retinoids or AHAs. Peptides are generally well-tolerated and low-risk.

Exfoliating Acids: AHAs, BHAs, and What Sets Them Apart

Chemical exfoliants work by loosening the bonds between dead skin cells so they shed more effectively — without the friction of a physical scrub. The two main categories are alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs), and their key difference comes down to solubility.

AHAs — which include glycolic acid, lactic acid, and mandelic acid — are water-soluble and primarily act on the skin's surface. They are commonly used to address dullness, uneven texture, and superficial hyperpigmentation. Lactic acid tends to be gentler than glycolic acid, which makes it a frequent recommendation for those new to chemical exfoliation.

BHAs, most notably salicylic acid, are oil-soluble. This property allows them to travel through the sebum that fills pores, making BHAs particularly effective for oily, acne-prone, or congested skin. Salicylic acid also has mild anti-inflammatory properties.

Both AHA and BHA use can increase sun sensitivity, so consistent SPF application is an important pairing. For a deeper look at how these acids compare to physical exfoliation, see chemical exfoliants vs. physical scrubs.

Retinoids: Vitamin A Derivatives

Retinoids are a family of vitamin A derivatives — ranging from over-the-counter retinol to prescription-strength tretinoin — and they have one of the strongest evidence bases of any topical skincare ingredient. They work by accelerating cell turnover, which over time can improve the appearance of fine lines, photoaging, acne, and texture irregularities.

The trade-off is that retinoids require gradual introduction. Starting with a low concentration used infrequently — then slowly increasing — helps minimize common side effects such as dryness, peeling, and temporary redness. Retinoids are also photosensitizing, so they are typically applied at night and paired with a daily broad-spectrum SPF.

Prescription retinoids should be used under the guidance of a licensed dermatologist. Over-the-counter retinol products are generally milder but still warrant a careful, measured approach — especially for sensitive skin types.

Understanding where each active fits into your routine is easier once you have a clear picture of the steps themselves. Our overview of what each skincare step is actually for explains how products layer and why sequence matters.

This article is for general informational and educational purposes only and is not medical or dermatological advice. Always consult a qualified healthcare professional before making changes to your skincare routine, particularly if you have a diagnosed skin condition or are pregnant.