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Summary The differential dignosis of asthma in farm workers is between a type I hypersensitivity to a pollen or dust allergen and a type III hypersensitivity to mould antigens. We describe asthma and rhinitis, and not farmer's lung, in a farming population due to the non‐pyroglyphid grain storage mite. Before a diagnosis of farmers' lung due to mouldy hay is made in any patient whether or not precipitins to Micropolyspora faeni are present, skin tests for storage mite should be made. If these are positive a diagnosis of ‘barn allergy’ should be considered and a trial of sodium cromoglycate be given.

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Summary Sera from 119 patients with possible food allergies were tested against a panel of thirteen food allergens by the RAST technique. The results were compared with in vivo tests. 79% of foods causing symptoms gave a positive RAST to the specific food. Symptoms were grouped according to their time of appearance after taking the food; ‘immediate’ up to 1 hr and ‘non‐immediate’ more than 1 hr afterwards. Almost all those with ‘immediate’ symptoms were already aware of the foods causing them and there was a 100% correlation of the RAST result with these. Only a few of those with ‘non‐immediate’ symptoms were previously aware that these foods were responsible, and 64% of these gave a positive RAST. The majority of patients with a positive RAST result had total IgE in excess of 300 u/ml, had specific IgE antibodies against one or more common inhalant allergens, were under the age of 30 years and had a combination of asthma and eczema. We found the RAST method a useful and safe guide upon which to base a clinical investigation of food allergy, especially for patients whose symptoms appeared more than 1 hr after the food and in whom the relationship between their symptoms and food was not apparent. The RAST technique was surprisingly successful in identifying the foods which caused these ‘non‐immediate’ symptoms.