Hay fever was well described by Blackley in 1973. The frequency of pollen asthma may be expressed as a percentage of general frequency of hay fever. The figure of Hagy and Settipane of 21% for students with a mean age of 17.9 years is quoted and ended with different results to the french study by Denis and Perdrizet of 6.5% in students with a mean age of 23 years. One may also express the frequency of asthma in subjects suffering from hay fever which vary greatly with the different plant families. The seasonal rhythm and the oculo-nasal accompaniment are very characteristic. The clinical "scores" of patients have been analysed in parallel with the atmospheric curves of pollen gathered. The current problems of hay fever are particularly: The problem of the penetration of the antigen into the bronchi, the methods of study are reviewed. Little pollen reaches the bronchi. In order to explain this paradox of pollen asthma vagal reflexes from the pharynx are involved and a possible penetration to the bronchi of fragments of pollen and above all aerosols containing allergens (Solomon). Why is it that certain patients have asthma and others only coryza? Perhaps the bronchial reaction is linked to different dose of antigen, to nasal obstruction which makes the subject breath with an open mouth, to different immunological phenomena more intensive in asthmatics than in the subject suffering from coryza (Kaliner) and the bronchial reactivity of certain subjects. In an inverse sense the allergy provokes or increased bronchial reactivity. Finally the early and delayed allergic responses to pollen are a model of what is an oedematous reaginic reaction then inflammatory.
