Relationship between the time of birth and the development of immediate hypersensitivity to grass-pollen antigens.

Eighty-six children aged three to 14 years were skin-tested for immediate hypersensitivity to antigens which are seasonal (grass pollens) or non-seasonal (car, dog, house-dust mite) in occurrence. Children who reached the age of three months during a time of environmental exposure to grass pollen demonstrated a significantly increased incidence of immediate hypersensitivity reactions to three grass pollens, as compared with children born at other times of the year. No significant difference was found in their reactions to the non-seasonal antigens. These findings indicate a relationship between the time of birth and the subsequent development of immediate hypersensitivity in childhood. It is suggested that infants are particularly susceptible to sensitization when presented with antigen around three months of age.