Skincare glossary

Carcinogen Category 2

EU hazard class meaning 'suspected of causing cancer' — the evidence is limited, usually from high-dose animal studies, not human exposure at cosmetic levels. Category 1 (proven human carcinogen) is far more serious; Category 2 is the 'can't rule it out at high doses' tier.

In practice, a Category 2 classification means regulators saw a signal in extreme-dose testing and want it watched. Concentration is everything: an ingredient can be a Category 2 carcinogen in pure industrial form and still be assessed as safe at 0.1% in a rinse-off product. Where a Category 2 substance appears in a legally sold EU/UK cosmetic, it sits within a concentration cap regulators have reviewed.

Chelator

An ingredient (like EDTA or citric acid) that grabs the minerals in hard water so your cleanser lathers and rinses properly instead of leaving a filmy residue.

CMR

Shorthand for Carcinogen, Mutagen or Reprotoxic — the EU's hazard classes for substances that could affect cancer risk, DNA or reproduction. The classification comes from high-dose studies, not the trace amounts allowed in cosmetics.

EU cosmetics law is stricter than general chemicals law here: CMR substances are banned in cosmetics by default, and a small number are only allowed by specific exemption at tightly capped concentrations after a safety review (SCCS opinion). If a product is legally sold in the EU/UK, any CMR-classified ingredient in it has passed that review at the dose in the bottle.

Comedogenic

Pore-clogging. A comedogenic ingredient can block follicles and lead to blackheads and breakouts in acne-prone skin. Ratings come from older rabbit-ear studies, so we treat them as a signal, not a verdict.

Contact time

How long an ingredient actually sits on your skin. A cleanser rinses off in about a minute, so even strong actives get little time to work. Leave-on products (serums, moisturisers, sunscreen) are where actives earn their keep.

Fungal acne

Not really acne — it's an overgrowth of the malassezia yeast in hair follicles. Looks like small, itchy, same-sized bumps. Regular acne treatments often make it worse, which is why it gets misdiagnosed for years.

Hard water

Tap water high in calcium and magnesium. It makes soap-based cleansers form a scummy film that stays on your skin, and it can leave skin feeling tight and squeaky in a bad way.

Humectant

A water-magnet ingredient (glycerin, hyaluronic acid, urea) that pulls moisture into the upper skin layers. Works best when sealed in by an occlusive on top.

INCI list

The official ingredient list on the pack (International Nomenclature of Cosmetic Ingredients). Ingredients are listed in descending order of concentration until 1%, after which they can appear in any order — that's why position on the list matters so much.

Malassezia

The yeast behind fungal acne (also called pityrosporum folliculitis). It lives on everyone's skin, but in some people it overgrows and causes itchy, uniform bumps — usually on the forehead, chest and back.

Malassezia food sources

Ingredients the fungal-acne yeast can literally eat. This yeast can't make its own fatty acids, so it feeds on certain oils, fatty-acid esters and ferments in your skincare. Formulas rich in those ingredients can trigger flare-ups if you're prone to fungal acne.

The science: malassezia can only metabolise fatty acids in the C11–C24 carbon-chain range, plus their esters (think anything ending in -ate, like isopropyl myristate), most plant oils, waxes, polysorbates and ferments. Very short chains (C8–C10, like caprylic/capric triglyceride) and fatty alcohols are safe — the yeast can't use them. We check every ingredient list against published guidance on exactly these families.

Mutagen

A substance that can damage DNA in lab testing. Like carcinogen classes, mutagen categories are assigned from high-dose studies — they signal 'worth watching', not 'dangerous at the levels used in cosmetics'.

Occlusive

An ingredient that forms a seal over skin (petrolatum, dimethicone, shea butter) to stop water evaporating. Doesn't add moisture itself — it locks in what's already there.

PA rating

The Japanese/Korean measure of UVA protection, printed as PA+ to PA++++. SPF tells you about burning (UVB); PA tells you about the deeper, ageing rays (UVA). PA++++ is the highest grade.

Pilling

When a product rolls up into little flakes or bobbles as you rub it in or layer over it — usually from film-formers and silicones clashing. Cosmetic, not dangerous, but it ruins makeup.

Reformulation

When a brand quietly changes a product's ingredient list while keeping the same name and packaging. We track formula versions so an old glowing review doesn't vouch for a new, different formula.

Reprotoxic

A substance suspected of affecting fertility or development in high-dose studies. EU cosmetics law bans or tightly caps such ingredients; at the permitted trace levels, exposure is far below the doses that raised concern.

Studied range

The concentration at which an ingredient actually showed results in published research. We compare each serum's likely dose against this range — a great ingredient at the wrong dose is just label decoration.

Surfactant

The cleansing agent in a wash — it lets oil and grime mix with water so they rinse away. Gentle surfactants clean without stripping; harsh ones (like sulfates) can wreck your barrier with daily use.

Two-source verified

Our highest ingredient-data grade: the INCI list was confirmed by two independent sources (for example the brand site plus a retailer), or straight from a pack photo. Single-source lists are marked as lower confidence.

Underdosed

When the thing a product is bought for is dosed too low to do the job — a serum whose hero active sits below the studied level, or a product sold as a sunscreen with SPF under 30. It is on the label for marketing, not for effect.

White cast

The pale or grey film some sunscreens leave on skin, caused by mineral UV filters (zinc oxide, titanium dioxide) scattering visible light. Far more visible on deeper skin tones — which is why we break this rating down by skin tone.