A British teenager who had a habit of chewing her hair died after a hairball, 12 inches long and 10 inches wide, developed in her stomach. The teenager died after several days of illness. It is thought that the hairball had irritated the lining of her stomach and hours after the operation she suffered massive bleeding.

It was only after she was admitted to hospital that it was discovered that the hairball had developed in her stomach. The medical diagnosis for the condition is called trichobezoar. Trichobezoars develop over a number of years as hair, which is indigestible, is swallowed and then becomes matted, slowly growing into a ball.

Dr Nera Patel, a pathologist, said the teenager's stomach wall had become irritated by the hairball and she had bled from a number of places. He said: "I had never encountered one before. No one in our medical team, of some 30 years' experience, had seen anything like it before. It is very rare." John Lyttle, a consultant surgeon, said that surgery was inherently "dangerous" and there was a 20 per cent death rate with stomach operations.

Bezoars are balls of indigestable matter that gradually build up in the stomach over a number of years. They can be made from a variety of things including fruit and vegetable matter (Phytobezoars). Occasionally bezoars can develop from stomach flora and fauna like Candida (Mycotic bezoars).

Trichobezoars are perhaps the most common type of bezoar to develop, although this is a rare condition. Trichobezoars develop in people who eat their hair, a condition called trichophagia. Trichophagia is generally regarded as a personality disorder similar to finger nail biting. In turn, trichophagia is often linked to habitual hair plucking which is called trichotillomania.

Trichobezoars are composed of hair, usually plucked from the individual's own scalp. The ingested hair always turns black, regardless of the original color, due to denaturation of proteins by the highly acidic stomach gastric juice. When a trichobezoar is removed in surgery it smells rather foul because the hair mesh traps undigested dietary fat and bacteria colonize the bezoar.

Up to 90% of patients with trichobezoars are female with many between 20 and 30 years of age. Reviewing 131 collected cases for symptoms associated with trichobezoars, a palpable abdominal mass was present (87.7%), abdominal pain (70.2%), nausea and vomiling (64.9%), weakness and weight loss (38.1%), constipation or diarrhoea (32%) and haematemesis (6.1%). The clinical symptoms of a trichobezoar vary considerably from person to person, and the size and position of the trichobezoar in the intestines.