Skincare Terms

The acid mantle is the skin's naturally slightly acidic surface environment. It helps support barrier enzymes, normal shedding, and microbial balance.

Acne cosmetica means acne-like clogged bumps triggered or worsened by products that repeatedly sit on acne-prone skin, including makeup, skincare, sunscreen, or hair-care residue.

Acne mechanica is acne or acne-like breakouts triggered by repeated friction, pressure, heat, or occlusion against the skin.

Anhydrous means a formula is made without water. In skincare, that usually means oils, balms, waxes, sticks, or powders rather than water-based creams or gels.

Anti-inflammatory means reducing or modifying inflammation. On a skincare label, it may describe evidence around an ingredient, but it does not automatically mean the finished cosmetic treats an inflammatory skin condition.

An antioxidant is an ingredient that helps neutralise reactive molecules called free radicals before oxidative stress can damage skin lipids, proteins, or DNA.

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.

Chemical sunscreen means sunscreen that uses organic UV filters - carbon-based sunscreen actives - to absorb ultraviolet radiation instead of relying only on mineral filters like zinc oxide or titanium dioxide.

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.

Comedolytic means an ingredient or treatment helps prevent or reduce comedones, the clogged pores involved in blackheads and closed comedones.

A comedone is a clogged hair follicle in acne-prone skin. Open comedones are blackheads, while closed comedones are often called whiteheads or closed bumps.

Critical wavelength is a sunscreen test value used to judge how far its UV protection extends into the UVA range. In the U.S. FDA broad-spectrum test, 370 nm or higher qualifies as broad spectrum.

Dehydrated skin means the outer skin layers are short on water or not holding water well. It can happen in dry, oily, or combination skin.

Double cleansing means using two cleansing steps, usually an oil-based or balm cleanser first and a gentle water-based cleanser second. It is useful for heavy sunscreen or makeup, but not mandatory for everyone.

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.

Erythema means visible red-to-purple colour caused by increased blood flow in superficial vessels, often with inflammation, heat, irritation, or skin disease.

Exfoliation means removing or loosening built-up dead cells from the skin surface or inside clogged follicles. Chemical exfoliants usually suit problem skin better than harsh scrubs.

A fatty alcohol is a waxy, long-chain alcohol used in skincare to soften texture, support emulsions, and improve product feel; it is not the same as drying alcohol.

Flushing means temporary redness and warmth caused by increased blood flow near the skin surface. In skincare, it often matters when heat, exercise, alcohol, spicy food, or rosacea make the face turn red quickly.

Fragrance-free means a product is marketed without added fragrance for scent, but you still need to read the ingredient list if you are sensitive or allergic.

Free radicals are unstable molecules that can damage skin lipids, proteins, and DNA when oxidative stress overwhelms the skin's normal defences. Antioxidants and sunscreen help reduce that stress.

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.

Hydrocolloid is an absorbent dressing material that takes up fluid and forms a soft gel. In skincare, it is best known as the clear material used in many pimple patches.

Hypoallergenic is a marketing claim suggesting lower allergy risk, but in U.S. cosmetics it has no federal standard definition or required FDA pre-approval.

INCI means International Nomenclature of Cosmetic Ingredients: the standardized naming system used for cosmetic ingredients so the same substance can be recognized across products and many markets.

Irritant contact dermatitis is inflammation caused by direct damage from repeated or strong exposure to an irritant. It is not an immune allergy, though it can look similar to allergic contact dermatitis.

Keratinization is the process where skin cells mature and form the outer skin layer. In acne, abnormal keratinization can make cells stick inside follicles and contribute to clogged pores.

A microcomedone is the tiny early clogged follicle that can develop before a visible blackhead, whitehead, or inflamed pimple appears.

Mineral sunscreen means sunscreen that uses inorganic UV filters, mainly zinc oxide and titanium dioxide, to help protect skin from ultraviolet radiation.

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.

Oil-free means a product is marketed as containing no oil ingredients. It can be useful for oily or acne-prone skin, but it does not automatically mean non-comedogenic or irritation-free.

Oxidative stress means reactive oxygen species outpace the skin's antioxidant defences. In skincare, it is usually discussed around UV exposure, pollution, inflammation, and visible ageing.

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.

A patch test is a way to check whether skin reacts to a product or allergen before wider use. Medical patch testing for contact dermatitis is different from a simple at-home product test.

Period after opening, or PAO, is the label time a cosmetic product is considered safe to use after you open it, commonly shown with an open jar symbol and a time such as 6M or 12M.

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.

Polyhydroxy acid, or PHA, means a hydroxy acid family used in skincare for gentle surface exfoliation and hydration-supportive smoothing. Gluconolactone and lactobionic acid are common examples.

A preservative is an ingredient used mainly to inhibit microbial growth in a cosmetic product, especially water-based formulas used repeatedly over time.

Product pilling is when skincare, sunscreen, or makeup rolls into tiny flakes or balls instead of forming a smooth layer on the skin.

Purging is the informal skincare term for a temporary acne flare that can happen when a treatment speeds up clogged pores already forming under the surface. Irritation is different and needs a calmer routine.

Razor bumps are inflamed bumps that happen when shaved or plucked hairs grow back into the skin and trigger irritation.

Retinization is the adjustment period when skin adapts to a retinoid, often with temporary dryness, flaking, stinging, or redness.

Rhinophyma is progressive thickening and enlargement of the skin and oil-gland tissue on the nose. It is a form of phymatous rosacea and is not proven to be caused by alcohol.

Sebaceous filaments are normal oil-flow structures inside pores, often visible as tiny grey, tan, or yellow dots on the nose. They are not the same as blackheads.

Sebum is the oily lipid mixture made by sebaceous glands and released onto the skin surface. It helps protect and lubricate skin, but too much visible sebum can contribute to shine and clogged pores.

Sebum oxidation means oils on the skin surface react with oxygen, UV, or pollution and form oxidised lipids that can irritate acne-prone skin.

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.

A skin protectant is an ingredient or OTC product category used to temporarily protect minor irritated, chapped, cracked, or exposed skin from further irritation.

Skin sensitization is the immune process by which a person becomes allergic to a substance after exposure, so later contact can trigger allergic contact dermatitis. It is different from ordinary irritation.

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.

The stratum corneum is the outermost layer of the epidermis. It helps keep water in, slow irritants from getting in, and make the skin barrier behave like a barrier.

A surfactant is a surface-active ingredient that helps water mix with oil, sweat, sunscreen, makeup, and dirt so a cleanser can rinse them away.

Telangiectasia means a small, widened blood vessel visible near the skin surface. In rosacea, these fine lines often appear around the cheeks and nose, though they can be difficult to see in darker skin.

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.

The UV Index is a standardized forecast or measurement of sunburn-weighted ultraviolet radiation at the Earth's surface. Higher numbers mean stronger UV and less time before unprotected skin may be harmed.

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.

UVA protection factor, often written UVA-PF or UVAPF, is a test-based measure of how much a sunscreen reduces UVA-induced pigment darkening compared with unprotected skin. It complements SPF, which mainly reflects UVB sunburn protection.

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.

White cast is the pale, grey, or chalky film some sunscreens leave on skin, especially mineral sunscreens with zinc oxide or titanium dioxide. It is a cosmetic finish issue, not proof the sunscreen is stronger or safer.