We are in the grip of an allergy epidemic. 50 years ago one in 30 were affected, but in Britain today it is closer to one in three. Horizon attempts to solve this medical puzzle. Show more
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We are in the grip of an allergy epidemic. 50 years ago one in 30 were affected, but in Britain today it is closer to one in three. Horizon attempts to solve this medical puzzle. Show more
BBC One
