Parthenium hysterophorus and Tanacetum parthenium, members of the Compositae family, are important causes of allergic contact dermatitis due to plants. Parthenium dermatitis is a major problem in India and Australia. Parthenium hysterophorus causes a spectrum of clinical patterns. Parthenium dermatitis, in its classical form known as airborne contact dermatitis, primarily affects the exposed areas and the flexures. Other clinical patterns are a seborrheic pattern, widespread dermatitis, and exfoliative dermatitis. The trend of the clinical pattern is changing. The classic airborne contact dermatitis may change to photodermatitis resembling chronic actinic dermatitis or mixed pattern dermatitis. The allergens responsible for contact dermatitis are sesquiterpene lactones and are present in the oleoresin fraction of the leaf, the stem, and the flower and also in pollen. The allergens can be extracted in various solvents (such as acetone, alcohol, ether, and water) and then used for patch testing. Acetone extract of Parthenium is better than aqueous extract in eliciting contact sensitivity. Treatment of Parthenium dermatitis is mostly symptomatic. Topical steroids, antihistamines, and avoidance of Parthenium are the mainstay of treatment for localized dermatitis. Systemic corticosteroids and azathioprine are frequently needed for severe or persistent dermatitis.