Hyposensitization To Environmental Allergens

Filed under: 4 - Atopic Dermatitis

It is not possible to avoid some environmental allergens, so that the question of hyposensitization naturally suggests itself. “Walker^“ in 1918 was the first to discuss this. He said: “Eczematous patients tolerate very small doses of the offending protein and the eczema seems to improve; but a slight increase makes the eczema worse. The amount of protein that benefits eczema is too small to prevent asthma, and the amount that benefits asthma makes the associated eczema worse. Desensitization for eczema must be a very slow and cautious process.” This was written thirty-seven years ago. It was true then; it is true now.

There is, however, considerable dif­ference of opinion as to the value of hyposensitization. Some place it on a par with hyposensitization in hay fever; some believe that it is worth­less. All are agreed with Walker’s original statement that very small doses of antigen must be used if exacerbations of the dermatitis are to be avoided. A severe exacerbation is no light matter, and it may be a good while before it calms down.

It has seemed to me that while hyposensitization is sometimes worth while, it can be by no means put upon the same plane as hyposensitiza­tion in hay fever. The situation is quite different. In hay fever the symptoms are brought about by local contact of pollen with the nasal mucosa; in atopic dermatitis due to pollen the pollen antigen has been ab­sorbed and brings about its effects from within.

If it is admitted that circulating pollen antigen causes the trouble, it is not logical to expect good results by adding more antigen to that which is already present. For this reason I am somewhat doubtful of the beneficial effects of such inocu­lations while the patient is still in his dusty house or during the pollen season. However, these are all ob­scure matters, with many questions un­answered, and I am sure that hypo­sensitization may sometimes do good. I have seen some patients made much worse by the injection of only a very small dose; I have seen some for whom attempted hyposensitization did no harm or no good; and I have seen a few where it was undoubtedly of real benefit.

For pollen dermatitis it is the only thing that can be done, except local treatment or treatment with cortisone. In the last two years I have given the inoculations intracutaneously rather than subcutaneously. Whether this is really any better than the subcutaneous method, I do not know. My recent practice has been to give once a week (later every two weeks) just enough extract (dust or pollen) to produce a reaction about as big as a nickel. In two pa­tients being treated now this is brought about by the injection of about 0.05 c.c. of a 1 to 10,000 pollen extract. The dose is not increased- no attempt is made to attain a maxi­mum tolerated dose as there is in treating hay fever; if you keep rais­ing the dose you will almost certainly reach the point where there will be an exacerbation of the eczema. I have taught one mother to give these intracutaneous injections-the dose is so small that there is no possibility of a general shock reaction.

Of the children with atopic derma­titis from wool whom I have seen, I have used hyposensitization in only three. These patients had such severe eczema that it was incapacitating. The dosage of wool extract used was 0.20 to 0.40 c.c. of a 1 to 10,000 dilu­tion given subcutaneously. One of these patients had a severe flare-up after a dose of 0.05 c.c. of a 1 to 1,000 dilution. It seemed to me, and to the patients, that hyposensitizing inocula­tions, which were done for several years in each case, were of definite benefit. The inoculations were started in September, carried through the winter, and discontinued in the sum­mer.

-Walker, I. C.: Causation of Eczema, Urticaria and Angioneurotic Oedema by Pro­teins Other Than Those Derived From Foods, J. A. M. A. 70: 897, 1918.

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