In a series of studies1 on the sensitivity of the skin to scarlatinal streptococcus filtrate toxin and its neutralizing antibody, the following facts have been observed:
In the new-born, the skin was usually not sensitive to considerable amounts of scarlatinal toxin, and this lack of sensitivity was not due to the presence of antitoxin in the blood. Relatively few infants developed sensitivity during the early months of life, but by the end of the first year the skin had become sensitive in a large proportion. Although antitoxin was not demonstrable in many young infants whose skin was insensitive to toxin, in older children the lack of sensitivity was practically always accompanied by antitoxin in the blood.
Hemolytic streptococci isolated from young infants with infections of the upper respiratory tract in certain instances formed a toxin which was neutralized by convalescent scarlet fever serum, but not by serum
COOKE JV. VIII. THE ANAPHYLACTIC FACTOR IN SCARLET FEVER. Am J Dis Child. 1928;35(6):991-1000. doi:10.1001/archpedi.1928.01920240038006