THE CUTANEOUS REACTION TO EGGWHITE

A study of 400 allergic patients of all ages, who were skin tested with eggwhite, is reported. The authors agree with those who believe that a positive reaction in infants who have in no known way been exposed to eggwhite after birth is in all probability due to intrauterine sensitization. There is a possibility, however, that some reactions to eggwhite may be due to a primary histamine or serotonin releasing substance present in the eggwhite which has no relationship to antigen-antibody reaction. The circumstances under which this takes place are not known. In all age groups the family history was positive in about 65% of cases. It was surprising to find, in view of previous opinions, that in the youngest age group (infants up to 2 years of age), the skin test was positive in less than half the patients (42%) in the presence of clinical sensitivity. It was also unexpected to find that the number of patients clinically sensitive to eggwhite but giving negative skin tests increased as age advanced. This justifies the common practice of eliminating egg as a trial measure in the diet of the first age group, regardless of the results of skin testing, and suggests that this should be done in any age group where food is considered a possible etiologic factor. In the youngest age group somewhat more than one-third (34%) of the patients reacted positively to eggwhite but were not clinically sensitive. This finding was completely unexpected as it had been thought that in this age group a positive skin test to eggwhite was practically pathognomonic of clinical sensitivity. In this study more positive reactions in children to eggwhite were obtained (70.5%) than in a somewhat comparable series where the incidence was much less (20%). We attribute this to the fact that in our series both scratch and intradermal tests were made while in the other series only scratch tests were done. This reflects the greater sensitivity of the intradermal test. Only about half the patients of all ages who react to eggwhite are also clinically sensitive. Attention is drawn to a theory which explains why a positive cutaneous test to a food, as eggwhite, may be clinically significant in atopic dermatitis even though the test (wheal reaction) does not reproduce the type of dermatitis being studied. There was no definite evidence, because the number of cases studied is far too small, to indicate that the severity of asthma which may ultimately develop in infants not asthmatic at the time of skin testing is proportional to the strength of the initial reaction to eggwhite.