Skincare Terms

Broad spectrum means a sunscreen has tested protection across both UVA and UVB wavelengths. It is the label phrase that tells you SPF is not the only protection signal.

Comedogenic means something has the potential to contribute to comedones, the clogged pores behind blackheads and whiteheads. It is a risk signal, not a guaranteed breakout sentence.

An emollient is a moisturising ingredient that softens and smooths the skin surface by filling tiny gaps between dry skin cells. Oils, esters, fatty alcohols, and silicones often act this way.

A humectant is a water-binding ingredient that helps increase hydration in the outer skin layer. Common examples include glycerin, urea, sodium hyaluronate, and panthenol.

Non-comedogenic means a product is marketed as unlikely to clog pores or trigger comedones. It is helpful language for acne-prone skin, but it is not a universal guarantee.

An occlusive is an ingredient that forms a protective surface layer to slow water loss from the skin. Petrolatum, dimethicone, mineral oil, waxes, and some butters can act as occlusives.

PA rating is a UVA protection label system, developed in Japan, that uses plus signs to communicate UVA protection strength. More plus signs mean higher measured UVA protection.

pH measures how acidic or alkaline something is. In skincare, it matters because the skin surface is naturally mildly acidic and barrier enzymes work best in that environment.

Photostability describes how well a sunscreen filter or finished sunscreen formula keeps working after exposure to light. A photostable formula resists breaking down during UV exposure.

The skin barrier is the outer protective system that helps keep water in and irritants out. In skincare, people usually mean the stratum corneum and its lipids, natural moisturising factors, pH, and microbiome.

SPF, or Sun Protection Factor, measures a sunscreen's protection against sunburn, which is driven mostly by UVB exposure. It does not tell you the whole story about UVA protection.

Transepidermal water loss, often shortened to TEWL, is the water that evaporates through the skin barrier. Higher TEWL usually means the barrier is losing water more easily.

UVA is the longer-wavelength part of ultraviolet radiation. It penetrates deeper than UVB and is strongly linked with tanning, pigmentation, visible ageing, and long-term skin damage.

UVB is the shorter-wavelength part of ultraviolet radiation most closely associated with sunburn. SPF mainly reflects how well a sunscreen protects against UVB-driven redness.

Water resistant means a sunscreen has been tested to keep its labeled SPF after water exposure for a stated time, usually 40 or 80 minutes in US labeling. It does not mean waterproof.