Acrylates/c10-30 alkyl acrylate crosspolymer A synthesised film-forming agent which can be used in haircare or skincare, especially moisturisers, because it leaves a smooth feel.

Acrylates copolymer A synthesised ingredient used as a film-former and hair fixative.

Adenosine phosphate Used to bind water and moisture in a product; it forms one of the building blocks of nucleic acid, which has a vital role in cell metabolism.

Algin A type of carbohydrate, derived from brown seaweed.

Alumina A derivative of aluminium which occurs in nature as bauxite or corundum, and is used as an anti-caking and bulking agent. It has no known skin toxicity, but high concentrations of alumina can be irritating if breathed in – more likely, we have to say, for an alumina miner than even the most slavish of cosmetic ‘junkies’ (especially if you’re encountering alumina in a lotion or cream rather than a powder form…)

Alcohol denat ‘Denat’ (which is short for ‘denatured’) means that the alcohol has been altered, so that it can’t get you drunk, or inebriate you in any way. (Believe it or not, in some ‘dry’ countries, perfume – for instance – is drunk by some very desperate people!) It’s derived from the fermentaton of starch, sugar and similar carbohydrates, and is used in a wide range of products including toners, suntan lotions, perfumes and acne products. Alcohol can be drying to the skin, as it has strong grease-dissolving powers.

Allantoin A botanical ingredient derived from comfrey, which is healing, soothing and anti-irritant, and may aid the healing of damaged skin.

Alpha glucan oligosaccharides This is obtained from natural sugars (sucrose and maltose), through the use of enzymes.

Alpha-isomethyl ionone A synthetic fragrance, generally used in tiny amounts (as are most fragrance ingredients). According to the Environmental Working Group’s Skin Deep Cosmetic Safety Database, this is a ‘Low hazard’ (it scores 2/10). It is also used as a food additive. This has to be listed on labels because this fragrance element has been linked, in some cases, to skin sensitivity.

Alpha-lipoic acid Used as a powerful antioxidant in skin creams ‘to fight age damage’, and derived mainly from dietary sources such as brewer’s yeast.

Aluminum chlorohydrate A salt derived from aluminium, which is considered by cosmetics manufacturers to be one of the least irritating aluminium salts (although in some people it can cause irritation, especially on shaved or abraded skin). It is one of the most frequently used anti-perspirant ingredients.

Aluminium hydroxide A mild alkaline astringent form of aluminium which is generally used in toothpaste, antiperspirants and dusting powders, with no known skin toxicity. It is also used in bread-making.

Aluminium stearate A form of stearic acid used as a thickening agent and to regulate a product’s stability, primarily in soaps, and also as an anti-caking agent in (for instance) instant coffee.

Aminomethyl propanediol Synthetically-derived crystals from nitrogen compounds, this is a kind of alcohol mostly used in hair products to adjust pH, or as an emulsifier.

Ammonium acryloyldimethyltaurate/vp copolymer Synthetic, film-forming thickener and stabilising ingredient, for all sorts of products: hand creams, sunscreens, foot creams, body lotions and facial moisturisers.

Ammonium alum Colourless, odourless, water-soluble ingredient derived from an ‘earth mineral’; no specific harmful effects have been noted in cosmetics and it is also found in small quantities in many of the foods we eat. A powerful anti-bacterial, often used in deodorants/anti-perspirants.

Ammonium glycyrrhizate Another name for Licorice root, this helps to form gels, stabilise emulsions – and is also used to soothe skin irritations and regulate pH levels.

Amodimethicone A synthetic polymer-like ingredient with skin-softening and conditioning – see also Dimethicone under ‘D‘ – here.

Amyl cinnamal A fragrance ingredient; Cinnamal is one of the most common allergens, and must be listed as a separate fragrance component on labels because of this.

Anisyl alcohol A fragrance ingredient which has been cited as ‘a moderately frequent cause of allergic contact dermatitis’, according to the Department of Dermatology, UCSF School of Medicine, San Francisco, but likely to be present in incredibly low quantities in most products.

Arachidyl behenate A waxy alcohol made from Arachidyl alcohol and Behenic acid. Arachidyl alcohol is sometimes isolated from animal liver, while Behenic acid is a colourless, water-soluble element which can be sourced from seed fats, animal fats and marine animal oils.

Arginine A strongly alkaline amino acid, which is particularly useful for its softening effect in hair conditioners.

Ascorbyl glucoside An extremely stable form of vitamin C, used as an antioxidant.

Ascorbyl palmitate A salt of vitamin C, used as a preservative and antioxidant in creams and lotions.

Aspartic acid An amino acid that occurs naturally in sugar beet, sugar cane, molasses and other plants, although it can also be created synthetically (and there’s no way to tell from the label). Used to make skin smooth, and is most often found in products for dry skin.

Astaxanthin A yellow colouring which is found naturally in animal organisms, and is used as a fish food for salmon to give that characteristic pink shade. Allowed as a general food colouring, and used in cosmetics as a colourant and also to boost skin’s condition.

Azo dyes Azo pigments are colourless particles (typically earths or clays), which have been coloured using an azo compound. Azo pigments are important in a variety of paints including artist’s paints. They have excellent colouring properties, but there are some health question marks over azo dyes – mostly by inhalation, or from eating them (or from working closely with them – for instance in hairdressing, or the clothing industry). Some azo dyes can also be irritating to skin.