INTRODUCTION In susceptible persons the ingestion of phenolphthalein provokes a peculiar eruption of the skin. This eruption consists of a few widely scattered and numerous irregularly grouped polychromatic macular plaques, varying in diameter from that of a pinhead to several inches, varying in color from pink to bright red, dusky violaceous and deep purple; it is relapsing in course, chronic in nature and usually results in a protracted pigmentation of the affected areas of skin. Slight scaling may accompany the evolution of the lesions; a peculiar mottling is sometimes seen in the central zone of the macules; vesiculation, erosion and superficial ulceration may occur, more especially on the mucous membranes of the mouth and on the skin of the genitals; a burning sensation sometimes precedes and accompanies the appearance of the patches; moderate to severe itching may be a symptom during their evolution. The eruption, clinically, is a persistent multiform