The incidence and causative factors of atopic asthma and rhinitis in an Orkney farming community.

Fifty farming families on the mainland (the largest island) or Orkney were surveyed to assess the amount of allergic respiratory disease and the principal causative factor. This account deals with only type I allergy and demonstrates a prevalence of asthma and rhinitis of 17.3% and of extrinsic asthma and rhinitis, in which definite allergic causes can be identified, of 12.7%. In addition it is shown that over one-fifth of the farming community are 'atopic' in that they demonstrate positive prick tests to one or more allergens. Less than 50% of those with allergic respiratory disease have attended the doctor with their complaint, a fact which calls in question the validity of epidemiological studies of allergic disease based on hospital and clinic attendances. Sex distribution confirms the finding that males suffer from asthma more frequently than females, however more females than males give positive skin tests without exhibiting symptoms of allergy. Pollens, animal danders and fungi all have a part to play in the aetiology of asthma and rhinitis among Orkney farmers, although the incidence of grass pollenosis is well below average. The two commonest allergens are hay dust and Dermatophagoides pteronyssinus which are found frequently to affect the same subject.