The Egg White Reaction
Filed under: 4 - Atopic DermatitisThe egg white reaction is so important in the atopic dermatitis of infants that it warrants special discussion. It has been found (Moro, Woringer, Hill) that most infants who have atopic dermatitis give strongly positive skin reactions to egg white, the majority of which are accompanied by circulating reagins and clinical sensitivity. Many of these babies are so exquisitely sensitive to egg white that the ingestion of only minute amounts is followed by stormy symptoms (urticaria, vomiting, shock). Horesh15 has pointed out, and with truth, that even the smell of egg white may cause symptoms, and that eczematous babies who are sensitive to it should be kept out of the kitchen when eggs are being broken for use in cooking. This is entirely right. Egg sensitivity lasts a long time, sometimes well into childhood. I have no accurate figures, but I doubt that it often lasts into adult life, and even in childhood its frequency is considerably diminished from what it is in infancy. It is a curious fact that in infants who have asthma, the egg white reaction is uncommon, unless the asthma is accompanied by eczema. The egg white reaction apparently has to do particularly with eczema. In a series of 100 asthmatic children, about half of whom had had eczema in infancy, twenty-one gave positive scratch tests to egg white, but only eleven were clinically sensitive to it.
J5Horesh, A. J.: Allergy to Food Odors, J. Allergy 14: 335, 1943.
A positive scratch test to egg white is of some value in differential diagnosis, for the chances are that if it is absent, what the baby has is not atopic dermatitis. This, however, is by no means certain, for some babies with atopic dermatitis give negative egg tests. I think the absence of a positive reaction is probably also of some prognostic value, and that one is justified in telling the mothers of such patients that the child is certainly not a highly allergic child, and that he has better than an even chance of escaping hay fever and asthma.
The direct influence of egg white in causing eczema in young babies is not great, for most mothers and doctors know enough now to keep it away from allergic babies. It is in this respect somewhat more important in older children whose diet is not so well controlled, and who may be eating enough egg-containing food to get into trouble.
While the actual eating of egg white is of little importance as a cause of eczema in most infants, I have a suspicion that the fact of egg sensitization may be of considerable importance. This is the primary sensitization for most of these infants. It is a sensitization of high degree, much more so than most of the others which follow it, and it has been thought, particularly by Moro, with whom I agree, that such sensitization, once it has taken place, makes the individual more susceptible to other sensitizations. It puts the stamp of allergy upon him-once he has become egg sensitive he has been admitted to the allergic fraternity, and is likely to continue his membership for a long time.
A good many years ago, Bret Kat-ner,16 after some painstaking laboratory work and considerable clinical observation, came to the conclusion that sensitization to egg white as it occurs in infants, and sometimes to other potent allergens such as fish and nuts, is congenital, and due to placental transmission of the allergen. This is active sensitization. I have always agreed with this. I do not see how it could take place in any other way, as most of these babies have never even seen an egg, let alone eating it. Some very competent allergists and immunologists have, however, disagreed, largely because positive skin tests to egg white are rarely obtained in newborn infants. One serious defect of their observations is that in order to arrive at any worth-while conclusions these tests should be done on a large series of infants whose mothers or fathers have hay fever-this has never been done. Testing the infants of normal mothers and fathers means but little, for it is largely the children of parents with hay fever who have eczema, and not so often those of normal parents.
It is true that often a baby, when tested at the second or third month, will have a negative egg white test, and when tested again at the sixth or seventh month it may be strongly positive in spite of the fact that he has not come into contact with egg during the intervening months. It is also often true that just about the time the egg white test becomes positive an eczema which has previously not amounted to much may turn into a very severe one, even to the erythrodermic point.
“Ratner, Bret: A Possible Causal Factor of Food Allergy in Certain Infants, Am. ,1. Dis. Child. 36: 277, 1928
These are the facts-the explanation is obscure. I think in the last year some light may have been shed on it. The young baby does not make gamma globulin as a rule until he is about 4 to 12 weeks old.17 What he has of it before this he has obtained from his mother. Until he can make his own gamma globulin he does not begin to make egg white antibodies, and until he does this he does not have a positive skin test to egg white. The weak point of this theory is that he has had no contact with the antigen since he was in utero. It is not known how long egg antigen may persist in the body, but it is well known that other protein antigens may persist for several months.
Sensitivity to egg white is such a common and such a striking phenomenon in infants with eczema, it is so much greater in degree than the other sensitizations which exist, and I have seen so many babies with a high degree of egg white sensitivity in whom no other sensitivity could be demonstrated that I have always had a suspicion that it may have something to do with the eczema even if there is no contact with the antigen (egg white). This is, of course, immunologic heresy, and I have no idea whatever how it might work.
17Dr. David Gitlin, Immunology Laboratory, Children’s Medical Center, Boston. Personal communication.
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