Although antihistamines were usually considered as ineffective in asthma, the appearance of new more potent anti-H1-antagonists with no or less side-effects leads to a reassessment of their use. Although mediators and mechanisms other than histamine are involved in natural or provoked reactions to allergens in the skin, the nose or the lungs, the new anti-H1-antagonists have been shown to be effective. For some of these drugs, the effect may go beyond a mere H1-receptor blockade and involve impairment of mediator release from mast cells and/or an inhibiting effect on other cell types (e.g. eosinophils) implicated in the late-phase reactions. Quantitative kinetics evaluation of late-phase reactions in the skin and of their inhibition by anti-allergic drugs will be helped considerably by the development of telethermography, a new skin evaluation technique.