A case of systemic mastocytosis with skin characteristics of telangiectasia macularis eruptiva perstans is reported. Systemic involvement was confirmed as a combination of highly increased urinary excretion of methyl imidazole acetic acid (Melm AA) and increased amounts of mast cells in skin, liver and colon transversum. Treatment with cimetidine (H2 receptor antagonist) resulted in diarrhea, however, the addition of cyproheptadine (H1 receptor antagonist) was beneficial in amelioration of the cutaneous symptoms of mastocytosis. The excretion of Melm AA was unchanged during treatment. After 7 months of continuous cimetidine and cyproheptadine treatment no side effects were observed.