Allergy planet.

With increasing numbers of allergy sufferers across the globe, Horizon asks why we seem to be becoming allergic to our planet. Mike and Sue Overtelly talk about their daughter's severe peanut allergy which sadly killed her. Even on remote islands there are an increase in numbers of people suffering with allergic conditions such as asthma. Noe Zamel has been tracing generations of asthma sufferers on the most remote island in the world, Tristan da Cunha. However, why have the numbers of asthma-sufferers grown so rapidly over the last 5 decades? Frank Gilliland is studying the effects of pollution in Southern California where allergy rates are extremely high. In the UK 14-year-old Billy Perkins suffers from Netherton syndrome, a severe skin condition which leaves him with a very thin epidermal layer. John Harper and Robin Callard from Great Ormond Street Hospital have discovered an important link between damaged skin layer and the incidence of allergy - this is likely why people with eczema also suffer from allergies. On the island of Bridgewater in Barbados the number of allergy sufferers has increased more rapidly than anywhere else in the world. Kathleen Barnes from John Hopkins University is researching possible causes for this increase in asthma sufferers - she believes it is largely due to the rapid changes that have enveloped the island community, taking them from a traditional lifestyle to the embrace of modern Western habits. Meanwhile cities such as Texas are home to a growing number of people who believe they have a condition called multiple chemical sensitivity (MCS), a condition not yet recognised by the American health authorities. Rebecca Knibb believes a large amount of people who think they have allergies are more likely to have intolerances. Lack of exposure to the allergen might paradoxically be a cause of severe allergies. 9-year-old Danny Peters has a rare and potentially fatal allergy to dogs. Adam Fox at St. Thomas' Hospital, London, uses immunotherapy with great success to treat him. And Gideon Lack is running a goundbreaking study in which young babies are fed peanuts from a very early age to see if this early exposure leads them to be more or less likely to be allergic to peanuts as they grow older.