Hair dyes are used by tens of millions of British women, and among all age groups and social demographics. Hair dye serves a number of purposes. Among those with greying hair, dyeing can knock years off their appearance and boost self-confidence. So too teenagers wishing to experiment with different colours and radical new looks often use hair dye to achieve their purpose. The main problem with hair dye is the fact that the most popular dyes contain various dangerous chemicals, especially Paraphenylenediamine (PPD). Chemicals such as PPD can cause allergic reactions, which range widely in their severity. PPD is actually banned in several European countries, but it is estimated the 75% of commercial dyes in the UK still contain the ingredient. They are popular because PPD-based dyes are commonly thought to achieve the most natural effect, and because the colour stays in the hair longer than with alternative dyes.

The number one cause of injuries from hair dyeing procedures is salons failing to conduct skin patch tests on new customers 24-48 hours before a treatment is due to be carried out. This test is aimed at identifying possible allergic reactions to chemicals contained in hair dye, by applying a small amount of the dye solution to a client's skin and monitoring the result. Serious allergic reactions to hair dye are usually classified medically as allergic contact dermatitis. This means that there is a risk of systemic problems affecting the whole body, as well as localised irritation and skin damage. One complicating factor is that people may become 'cross-sensitised' to chemicals contained in hair dyes from external substances (black Henna tattoos being one example). Once sensitised by a chemical such as PPD, a person may also suffer allergic reactions to other substances, including dyes contained in foods and certain local anaesthetics. This is known as 'cross-reactivity'.

It is difficult to estimate how many women (and men) experience allergic reactions to hair dye each year, because the majority do not seek medical attention. Symptoms of a mild reaction include a localised rash developing, but one which usually clears up within hours or days. With a more serious reaction a rash may spread across the face and/or scalp, and irritation of the skin will steadily worsen. Hives and blisters may start to form, and a burning sensation will be felt across affected areas. It is common for the face and particularly the eyelids to swell up, and indeed the eyes may close completely. These symptoms may be accompanied by nausea, and when the scalp is affected the hair may begin to fall out. In rare cases a person may experience respiratory problems caused by swelling of the tongue and constriction of the airways. In such circumstances emergency hospital attention will be immediately required.

Hair salon clients have a legal right to expect that their hair dyeing treatment will be carried out in a reasonably competent manner, by trained, experienced and skilled professionals. Negligence on the part of a hair salon includes failing to carry out skin patch tests on new clients, where the lack of such a test has precipitated an allergic reaction and damage to skin and/or hair. Apart from the emotional distress caused by injuries of this kind, they may also be physically disfiguring, either due to temporary or permanent baldness, or scarring to the face or scalp. An injured person may require costly corrective surgery, and may be forced to take a prolonged period of time off work due to the humiliation caused by their appearance. All such financial and emotional considerations are taken into account when calculating compensation awards for allergic reactions to hair dye treatments, as well as the physical pain and suffering caused.