Colours used in cosmetics and body care products generally fall into one of three basic categories: organic, inorganic and natural. (This refers to chemistry and should not be confused with the term 'organic', which refers to growing/production methods for food etc.)

Organic colours are derived primarily from petroleum and are sometimes known as 'coal-tar dyes' or 'synthetic organic' colours.

Inorganic colours include clays, iron oxides (which can produce yellows, browns, blacks and reds) and ultramarines (including chromium-oxide green, mica, titanium dioxide, zinc oxide and kaolin clay.

Natural colours are those that are derived from plant or animal sources. Although they can be from 'earth' sources, inorganic colours are not generally considered natural because they are heat-treated to various temperatures to produce different colours.

Some, like mica can be coated with organic colours to create a particular hue. In addition, while many oxides and ultramarines were mined in the past, because of concerns over purity (mined products can be contaminated with lead, arsenic, mercury, antimony or selenium), many of these colourants today are manufactured in a lab.

Checking for the presence of potentially harmful dyes in cosmetics is difficult because the same colours can be listed on the label under any number of different names.

In Europe colours are generally listed by their International Nomenclature for Cosmetic Ingredients (INCI) numbers, usually indicated by the prefix 'CI' followed by five numbers. In the US, the same colours are listed using an FD&C (Foods, Drugs and Cosmetics) or a D&C (Drugs and Cosmetics) prefix.

To add to the confusion, even the experts cannot agree on an international 'safe' list of colours. This means that some colours may be allowed in one country, but banned elsewhere. All this would not be important but for the fact that some cosmetic colours are known to cause problems in susceptible individuals.

Most organic colours can cause skin irritation and some can block the pores. Even inorganic mineral pigments - which are generally considered safer than petroleum-derived colours - can and do produce sensitivity reactions.

Iron oxides, for example, contain nickel and a large percentage of the population - around 18 per cent - has an allergy to nickel. More worrying is the fact that many commonly used organic colours have been shown to cause cancerous growths in the skin of animals. This may be either because the raw materials used to make them are carcinogenic or because of the presence of carcinogenic impurities in some batches.

Make up sold by Absolutely Pure contains ingredients shown in bold.