Lactic acid An Alpha-Hydroxy Acid (a.k.a. ‘fruit acid’) derived from milk; AHAs may cause sensitivity in the skin as they remove the outer cells.

Lactoperoxidase An enzyme from milk, sugar or whey, which is used as a moisturiser and to help regulate sebum production. Can help reduce clogged pores (blackheads).

Laureth-2 An ingredient synthesised from Lauryl alcohol. Ingredients like this – created by a process called ‘ethoxylation’ – canbe contaminated to produce 1,4-dioxane – a carcinogen – although that’s not to say they will be, provided effective controls are in place.

Laureth-3 As above, an ingredient synthesised from Lauryl alcohol.

Lauric acid Also known as n-Dodecanoic acid, find this in vegetable fats – in particular, laurel oil and coconut oil. It is the base ingredient in countless soaps, shampoos and detergents – think Sodium Lauryl Sulfate, Sodium Laureth Sulfate (and many others), because of its excellent foaming action. It can be a mild irritant but should not permanently sensitise skin; some experts say it can be pore-blocking.

Lauroyl lysine A derivative of Lysine, an amino acid, which is an excellent skin conditioning agent.

Lauryl glucoside A very mild surfactant which is increasingly widely used in natural cosmetics for its gentleness.

Lauryl lactate An Alpha-Hydroxy Acid (AHA/fruit acid) which can cause skin sensitivity.

Lauryl laurate A stabiliser and binder – see Lauric acid.

Lauryl peg-9 polydimethylsiloxyethyl dimethicone A synthetic silicone-derived surfactant (see Surfactant under ‘S‘ – here).

Lecithin A naturally moisturising ingredient from soya, sunflower seeds, egg yolks etc.

Levulinic acid This white, crystalline ingredient is prepared from inulin, starch etc., and is used as a fragrance ingredient and as an effective skin conditioner.

Limonene Naturally occurring in star anise, caraway, celery, oranges, cumin, fennel, marigold and more, this compound has to be listed on labels because it is one of the most common allergens.

Linalool A compound found in lavender oil which has to be listed on labels because it’s one of the most common allergens.

Lipo-filling complex (saccharomyces/xylinum , black tea ferment and hydroxyethylcellulose) This is a proprietary blend of ingredients (present only in an Avalon product, in The Green Beauty Bible) based on ingredients derived from sugar, black tea and cellulose. As a phrase, ‘Lipo-filling’ is pretty meaningless; in cosmetic surgery it’s the term used for fat injections, so we are assuming that Avalon use this to ‘plump up’ the skin.

Lycopene A powerful antioxidant (with a red colour), found in tomatoes, grapefruit, rose hips and paprika.

Lysolecithin A product obtained by treating lecithin with enzymes, usually to create a base for creams.