Glossary
The words you meet on sunscreen labels and in a dermatologist's notes, explained briefly and linked to the guides that use them.
- Azelaic acidAzelaic acid is an anti-inflammatory and antioxidant ingredient used for acne and rosacea. It also helps reduce pigmentation, which makes it useful for post-acne marks and melasma.
- MelasmaMelasma is a common, long-lasting pattern of brown or grey-brown patches, usually on both sides of the face, that sunlight, visible light and hormonal changes can make darker.
- NiacinamideNiacinamide, also called nicotinamide, is the water-soluble active form of vitamin B3. In skincare it is used to improve blotchiness and the look of pigmented spots.
- PA rating (PA+ to PA++++)The PA rating is a UVA protection grade, developed in Japan, shown as plus signs from PA+ to PA++++. More plus signs mean more UVA protection.
- Post-inflammatory hyperpigmentation (PIH)Post-inflammatory hyperpigmentation (PIH) is darkening that stays behind after skin has been inflamed or injured, for example by acne, eczema, a burn, waxing or a procedure.
- SPFSPF, or sun protection factor, mainly tells you how well a sunscreen protects against UVB, the rays that cause sunburn. On its own it says little about UVA.
- Tranexamic acidTranexamic acid is a medicine that slows the breakdown of blood clots. In skincare it is a topical ingredient studied for melasma; as a tablet it is a prescription medicine, not a supplement.
- UVAUVA is the longer-wavelength part of the sun's ultraviolet light. It passes through ordinary window glass and contributes to tanning, skin ageing and darker pigmentation.