Prostaglandin D₂ and histamine during the immediate and the late-phase components of allergic cutaneous responses

With a skin blister technique in which the mediators generated by the trauma of forming the blister are allowed to subside, we have collected human interstitial skin fluid during the course of allergic reactions to ragweed, and measured levels of histamine and prostaglandin D₂ (PGD₂). Of 18 ragweed-allergic individuals tested, 11 developed both an immediate and a late-phase reaction (LPR) with fivefold-elevated levels of histamine (40 ng/ml) at 30 minutes and a peak level of PGD₂ (6.5 ng/ml) later at 2 1 2 hours after ragweed challenge. The other seven allergic individuals had immediate reactions without an LPR lesion and demonstrated somewhat smaller elevations of histamine (25 ng/ml) but much lower levels of PGD₂ (1.6 ng/ml; p < 0.05). The time course of appearance of these mediators was identical in both groups of patients. The fluids from unchallenged blisters of allergic and nonallergic patients and the fluids of nonallergic patients challenged with ragweed had similar levels of histamine, at the lower limit of detection, and undetectable PGD₂ levels. The peak levels of PGD₂ in allergic individuals correlated with the size of the LPR lesion (p < 0.05). These data suggest that the LPR involves the secondary elaboration of mediators different from mediators responsible for the immediate manifestations of the allergic skin reaction.