CIRCADIAN-RHYTHM OF CUTANEOUS HYPERSENSITIVITY REACTIONS IN NOCTURNALASTHMA

Background: Diurnal variation in mast cell discharge may play a centra l role in the early morning fall in peak expiratory flow rate (PEFR) i n nocturnal asthmatic patients. Methods: We tested the hypothesis that there is a circadian rhythm in mast cell response to allergen in 15 p atients with nocturnal asthma by measuring the magnitude of cutaneous hypersensitivity reactions at 0600, 1200, 1800, and 2400 hours. Pre-ad mission, prick skin testing on the ventral aspect of the forearm to va rious allergens was performed. The allergen producing the largest whea l was tested at six sites on one forearm. Response was quantified afte r 20 minutes by measuring the area of the wheal produced using planime try. Every six hours the skin testing was repeated at six new sites on alternating forearms. The average area of the six wheals was calculat ed and recorded at each time. The prick skin technique was used at all times. Results: Maximal reactions occurred in 10 of the 15 patients a t noon (P = .031, Friedman's two way analysis of variance). In these 1 0 patients wheal area at the time of maximum reactivity was on average 3.3-fold higher than at the time of minimum reactivity. The mean whea l areas for all 15 patients at 0600, 1200, 1800, and 2400 hours were 3 4 mm(2), 42 mm(2), 34 mm(2), and 35 mm(2) respectively. Conclusions: T hese observations support the concept of a circadian rhythm in mast ce ll activity in patients with severe nocturnal asthma.