To explore the pruritogenic and inflammatory effects of cytokines, a single dose of 20 micrograms recombinant human interleukin-2 was injected intradermally into eight patients with atopic dermatitis and eight healthy controls. The study was double-blind and randomized with glucose as a negative control. The effects were evaluated by recording local itch and erythema over 72 h and by examining skin biopsies taken at 24 h and 72 h. In patients and controls, interleukin-2 provoked a low-intensity local itch with maximal intensity between 6 h and 48 h and erythema with maximal extension between 12 h and 72 h. In the atopic dermatitis patients, these reactions tended to appear earlier and were less pronounced than in the healthy controls. Interleukin-2 induced dermal mononuclear cell infiltrates consisting mainly of CD3+ cells. A majority of the T cells were CD4+. The number of dermal CD25+, HLA-DR+ and ICAM-1+ cells was also increased at the interleukin-2 induced spongiosis and exocytosis as well as HLA-DR+ and ICAM-1+ keratinocytes. The microscopic findings tended to be more prominent at 72 h than at 24 h in both groups, but with a somewhat slower onset in the atopic dermatitis patients. In conclusion, a single intradermal injection of interleukin-2 induced local itch, erythema, dermal T-cell infiltrates, spongiosis, exocytosis and activation of keratinocytes both in atopic dermatitis patients and in healthy controls.