Among a group of 131 young adults tested, there was a high degree of correlation between the occurrence of immediate skin reactions of the wheal and erythema type produced by purified diphtheria toxoid and personal or familial history of allergy of the hay-fever type.
Of 39 Schick-negative subjects who received a "booster" dose of purified diphtheria toxoid, 19 showed no immediate skin reactions before immunization. The development of skin sensitivity in these subjects was associated with the production of non-precipitating circulating antitoxin.
Three subjects produced 20 units or more antitoxin per cc. serum following immunization, without demonstrable precipitins. Despite the fact that none showed immediate skin reactions to Schick toxoid prior to immunization, all 3 possessed a high degree of skin sensitivity to toxoid following immunization.