Skin reactivity to codeine and histamine during prolonged corticosteroid therapy.

Corticosteroids, used in low to moderate doses for short time intervals, do not suppress immediate percutaneous skin test responses to allergens, compound 48/80, or histamine. During routine skin testing, in our clinic, intradermal injection of codeine (1 mg/ml) and histamine (0.02 mg/ml) are used as positive controls. We had noted that responses to codeine but not histamine are decreased in some patients with asthma who had been receiving prolonged corticosteroid therapy. Therefore, we retrospectively compared skin test responses to codeine and histamine between 25 adult subjects with asthma receiving steroids (group I) and 25 age-matched control subjects (group II). In group I, the mean wheal diameters, induced by codeine but not histamine, were significantly less than diameters in group II. This decreased skin test reactivity to codeine was not due to effects of theophylline also taken by group I subjects, since the skin test reactions of other subjects with asthma, treated with theophylline but not steroids (group III), were not significantly different from reactions in group II. We conclude that prolonged courses of corticosteroids do not appear to alter histamine-induced vascular reactivity in skin but may affect cutaneous mast cell responses by an undefined mechanism.