Is month of birth a risk factor for subsequent development of pollen allergy in adults?

A comparison of the date of birth of 1501 adult patients with severe seasonal respiratory allergy (allergic rhinitis or bronchial asthma) due to parietaria, olive, and grass pollens with the expected births within 2,020,420 births in South Greece during the same period, was performed. The relative risk for developing respiratory allergy was characteristically increased in those born in a specific period of time different for each pollen. The relative risk for parietaria was increased (1.47) in those born in March; for olive it was 1.6 for May; 1.2 for April; and 1.4 for March, while the relative risk for grasses was 1.2 in those born in June and July. These findings are indicative of the importance of the month of birth; that is, the early exposure to pollens, for the development of respiratory allergy to certain pollens during adulthood. Because our findings do not directly correlate completely with the aerobiology studies on pollen calculation in Athens' atmosphere, we supposed that other environmental factors, e.g., the local intensity of the first pollination or the influence of weather conditions, may contribute to the final development of respiratory allergy as well. The most impressive finding was the significant influence of the month of birth in the development of respiratory allergy due to parietaria and olive pollens during adulthood.