What does it actually do?

Hyaluronic acid

Also: sodium hyaluronate

Attracts water and holds it in the top layer of the skin, so your skin feels plumper and more supple. Light in texture, so suitable for every skin type.

Apply to slightly damp skin and follow with a moisturiser.

Glycerin

Also: glycerine

One of the most widely used and best-studied humectants. Not exciting, but very effective and usually well tolerated.

Ceramides

Also: ceramide NP, AP, EOP

Lipids that naturally occur in your skin barrier, like the mortar between bricks. Creams with ceramides help dry or sensitive skin hold on to moisture.

Niacinamide

Also: vitamin B3

A versatile ingredient that supports the skin barrier and can reduce visible redness, shine and pores. Usually well tolerated.

Higher percentages aren't necessarily better. Around 2 to 5% is often enough; sensitive skin in particular can react to higher doses.

Salicylic acid (BHA)

Also: salicylic acid

Oil-soluble, so it can work inside the pores. Helps with blackheads and oily, breakout-prone skin.

Start with two or three times a week. Wear sunscreen during the day.

Lactic acid (AHA)

Also: lactic acid

A mild exfoliant that loosens dead skin cells on the surface. Lactic acid also attracts a little moisture and is gentler than glycolic acid.

AHAs make your skin more sensitive to sun, so always use SPF during the day.

Retinol

Also: vitamin A, retinoids

Speeds up skin cell renewal. Well studied for fine lines, uneven skin and clogged pores. Can cause dryness and irritation at first.

Start with a low dose, 2 or 3 evenings a week. Don't use it if you are pregnant or breastfeeding, and wear SPF during the day.

Vitamin C

Also: ascorbic acid and derivatives

An antioxidant that helps protect your skin from external damage and can give dull skin a little more glow.

Works best in the morning under your sunscreen. Store it dark and cool; serum that has turned brown is less effective.

Zinc oxide

Also: zinc oxide, mineral filter

A mineral UV filter in sunscreen that gives broad protection and is usually gentle on sensitive skin. Can leave a slight white cast.

Panthenol

Also: provitamin B5

Soothes and holds moisture. Pleasant for skin that feels tight, chapped or has just been irritated.

Centella asiatica

Also: tiger grass, cica

A plant long used for irritated skin. Often found in soothing creams for red or sensitive skin.

Aloe vera

Also: aloe barbadensis

Cooling and lightly hydrating. Nice for warm, tight-feeling skin, for example after a day in the sun.

Choose a product without fragrance and without much alcohol.

Squalane

Also: squalane

A light oil similar to the lipids your skin makes itself. Absorbs quickly and doesn't feel heavy.

Shea butter

Also: butyrospermum parkii

A rich plant butter that forms a protective layer. Ideal for dry skin and dry patches in winter.

Best kept off the face if you have oily skin with blackheads.