The aerial distribution of the pollen grains Cassia species was found to be predominant in Kerala and Tamil Nadu, the adjacent states of South India. The present study deals with the allergenicity and biochemical aspects of four different species of Cassia which were found to be dominant in the atmosphere of India. The pollen grains of Cassia occidentalis were found to be the most and Cassia roxburghii the least reactive of the four different species studied. The individual analysis of the reactive patients also showed the possibilities of cross-reactivity. The protein, carbohydrate and amino acids of these members were analysed. The results obtained are useful as a step towards standardisation of allergen extracts of Cassia species and are also worthy of further investigations both in relation to cross-reactivity and characterisation of allergens.