Type I hypersensitivity toParthenium hysterophorusin patients with parthenium dermatitis

Parthenium dermatitis is a major problem in urban and rural India. Patients with severe allergic rhinitis due to exposure to pollens of parthenium are reported to have parthenium specific IgE and IgG antibodies. Parthenium induces contact dermatitis by Type IV hypersensitivity and allergic rhinitis by Type-I hypersensitivity.The study was undertaken to detect Type-I and Type-IV hypersensitivity amongst patients with parthenium dermatitis.Fourteen patients with clinical features of parthenium dermatitis who patch tested positive to parthenium were included in the study. Patch testing was done by standard method and results interpreted as recommended by the ICDRG. Serum IgE was determined by chemiluminescence immuno assay system (CLIA). Prick testing was performed and interpreted by standard method.Twelve out of the 14 patients included, showed a positive prick test. Serum IgE was elevated in all patients to varying degrees (mean IgE-1279.9 IU/ml; N--up to 100 IU/ml).The positive patch test, prick test and elevated serum IgE suggest that both Type-I and Type-IV hypersensitivity may play a role in the induction and perpetuation of parthenium dermatitis in most patients. To date, delayed hypersensitivity was thought to be solely responsible for parthenium dermatitis. This study suggests that a combined type-I and type IV hypersensitivity mechanisms may be operational.