An evaluation of the pharmacologic inhibition of the immediate and late cutaneous reaction to allergen

The effects of an H₁ antagonist (chlorpheniramine) and an H₂ antagonist (cimetidine) alone or in combination, and of ASA on the ICR and the LCR to timothy or ragweed were evaluated. HCRs were also applied at each testing. The H₁ blocker alone significantly inhibited the HCR and the ICR, but not the LCR. The H₂ blocker by itself had no effect on HCR, ICR, or LCR. The addition of the H₂ to the H₁ blocker markedly increased the H₁ blocker's inhibition of the HCR and ICR and completely obliterated the LCR in most subjects. These findings, which could not be explained by simple additive effects, suggest a synergistic activity of the H₁ and the H₂ blocker combination. ASA had no effect on HCR, ICR, or LCR, casting doubt on the possible role of prostaglandins in the LCR.