Allergic diseases such as bronchial asthma, allergic rhinitis and atopicdermatitis are dramatically increasing all over the world including developing countries like India.Today, more than 30 % of the population is known to suffer from one or other allergic ailment. Majorcausative agents implicated are pollen grains, fungal spores, dust mites, insect debris, animal epithelia,etc. Several aerobiological studies have been conducted in different parts of the country to ascertainaerial concentration and seasonality of pollen grains and fungi. Recently, an All India CoordinatedProject on Aeroallergens and Human Health was undertaken to discover the quantitative and qualitativeprevalence of aerosols at 18 different centres in the country. Predominant airborne pollen are Holoptelea,Poaceae, Asteraceae, Eucalyptus, Casuarina, Putanjiva, Cassia, Quercus, Cocos, Pinus, Cedrus, Ailanthus,Cheno/Amaranth, Cyperus, Argemone, Xanthium, Parthenium and others. Clinical and immunological evaluationshave revealed allergenically important texa - some of them for the first time. Allergenically importantpollen are Prosopis juliflora, Ricinus communis, Morus, Mallotus, Alnus, Querecus, Cedrus, Argemone,Amaranthus, Chenopodium, Holoptelea, Brassica, Cocos, Cannabis, Parthenium, Cassia and grasses. Furthercross-reactivity of the IgE antibodies is a common phenomenon among various pollen allergens. Ricinuscommunis pollen from commonly growing weeds in India, cross-reacts with latex (Hevea brasiliensis), Mercurialisannua and also with seeds of Ricinus communis - all belonging to family Euphorbiaceae. Areca catechucross-reacts with other members of Arecaceae such as Phoenix sylvestris, Cocos nucifera and Borassusflabelifer. Several reports on pollen and fruit syndrome have been analyzed. Experiments conducted byus revealed that pollutants (NO(2) and SO(2)) not only affect pollen morphology but also changes theirallergenic potency. Immunotherapy with recombinant proteins having similar epitopes from different allergenshave been advocated, besides allergen avoidance.