SummaryA case of pigmented purpuric dermatosis is reported. The patient was a fit young girl subject to recurrent, generalized, transient purpuric capillaritis appearing 36–55 hr after systemic absorption of house‐dust mite antigen. Her serum contained IgG and IgE antibodies to house dust and to mite antigens. Skin from a test site had IgE on the mast cells, and half of the cells showed anaphylactic degranulation. However, this case was not a typical example of anaphylactic (atopic) sensitivity, and did not resemble any of the classical types of allergy.