Parthenium hysterophorus is the commonest cause of airborne contact dermatitis in northern India. Treatment is mostly palliative and consists of repeated courses of antihistamines and topical and/or systemic corticosteroids. We have evaluated the effect of oral hyposensitization as an alternative therapeutic modality. In 70% of those patients who completed the study, there was a gradual improvement in their clinical status, as evident from a fall in their clinical severity score for eczema. 30% of patients had an exacerbation during the course of the study and hence hyposensitization in them was stopped. Patients tolerated therapy well and no significant side-effects were seen, except for abdominal pain, 'heartburn' and cheilitis.