Solanidine and tomatidine trigger scar pruritus.

Scar pruritus is frequently encountered in clinical practice (particularly in burn patients) owing to its poorly known pathogenesis and difficult treatment. In previous work, we demonstrated the usefulness of a diet excluding edible solanaceae (viz., potatoes, tomatoes, peppers and aubergines) in patients with antihistamine-resistant scar pruritus. We hypothesized that alkaloids in solanaceae (particularly their secondary metabolites or aglycones) might be the actual pruritogens. In order to test this hypothesis, we conducted a single-blind prospective study on patients responding favourably to a solanaceae-free diet whose scar pruritus could be ascribed to one of the four foods. The study involved applying the aglycones solanidine and tomatidine to each scar and checking whether, and which, had a pruritogenic effect. A total of 18 patients (90%) responded by developing pruritus; also, the triggering aglycone coincided with that prevailing in the pruritogenic food. We concluded that solanaceae aglycones are directly involved in the pathogenesis of scar pruritus.