Summary Serum levels of total and specific immunoglobulin E (IgE) have been determined by radioimmunoassays in sixty‐nine allergic subjects. The forty‐one subjects with mild symptoms were the most difficult to diagnose, since nine had IgE levels less than 50 U/ml and nineteen had no detectable specific IgE antibodies. Samples of nasal secretions were collected from these nineteen subjects and five were found to have specific IgE antibodies, and in a further eight increased amounts of total IgE. The possibility of locally produced IgE antibodies should therefore be considered when using in vitro tests to diagnose mild or recently acquired allergies, especially when serum IgE levels are less than 50 U/ml.

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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.

Eighty adult asthmatics living in an African city had a significantly higher serum IgE level (799 u/ml) than the control group (350 u/ml). A high proportion (78-7%) of the asthmatics had demonstrable circulating mite-specific IgE antibodies. The rural population of a filariasis endemic region was investigated and although no allergic subjects were identified, the group had a significantly higher IgE level (1613 u/ml) than the asthmatics and also showed a relatively high incidence of grass pollen-specific IgE antibodies (35%). The discrepancy between clinical history and laboratory results supports the mast cell saturation hypothesis and suggests: (a) an explanation for the susceptibility to allergy of African and Asian immigrants to Great Britain, and (b) a practical approach for preventing allergic reactions in vivo.

Summary The Phadiatop® test, which is based on a multi‐allergen allergosorbent, proved to be a test that is simple to perform in the laboratory and produces reliable results. When compared with the more conventional RAST atopy screening test for grass, mite and IgE antibodies it produced similar results, except in those rare instances of patients who were RAST‐positive only for moulds where the Phadiatop test was decidedly superior. The Phadiatop test disc contains only inhalant allergens and so it could not be used for screening infants and very young children whose IgE response, if any, is probably limited to foods.