Immunodeficiency including HIV During the past 10 days before start of treatment and during the study Topical steroids H2 antihistamines Leukotriene antagonists H1 antihistamine other then basic therapy During the past 2 weeks before start of treatment and during the study Ketotifen Doxepin During the past 4 weeks before start of treatment and during the study Systemic corticosteroids UV therapy including PUVA Systemic immunosuppressives including corticosteroids, immunomodulators, immunostimulants During the past 12 weeks before start of treatment and during the study Astemizole Tranquilizers, antidepressants, sedatives, hypnotics, antiepileptics and other CNS active agents, except treatment with tricyclics that is stable for at least 12 weeks prior to screening and throughout the trial