Clinico-immunologic evaluation of allergy to Himalayan tree pollen in atopic subjects in India--a new record.

Exposure to local pollen allergens has a direct bearing on the prevalence of allergic symptoms among the inhabiting atopic population. The populations in the Himalayas and around it are exposed to a variety of pollen grains from trees growing in the region, but the pollen-population interaction has not been clinically investigated. Himalayan tree pollen from five different taxa, i.e. Alnus nitida (AN), Betula utilis (BU), Cedrus deodara (CD), Mallotus phillipensis (MP) and Quercus incana (QI) were evaluated for their allergenicity in the Indian population by in vivo (skin prick test) and in vitro (ELISA) clinico-immunological methods. The presence of specific IgE against these tree pollen in the sera of skin test positive patients was taken as evidence for sensitization to these pollen. The average skin positivity in atopic populations recorded at different allergy centers in India varied from 2.2% against AN, to 4.7% against MP pollen. Significantly raised specific IgE against these pollen were observed in the sera of hypersensitive patients. The sensitization pattern to Himalayan tree pollen in these atopic populations varied. It was concluded that skin prick test positivity and raised IgE antibodies specific to AN, BU, CD, MP and QI established Himalayan tree pollen as important sensitizers in the atopic populations of India. A high incidence of skin sensitivity was observed to pollen antigens of Cedrus deodara, Mallotus phillipensis and Quercus incana in patients of Chandigarh residing in the hills and foothills of the Himalayas while Alnus nitida, Betula utilis and Cedrus deodara were important sensitizers in Delhi patients. The skin sensitization pattern against these pollen was in accordance with the level of exposure to these pollen of the subjects residing in that part of the country.