Seborrhoeic dermatitis usually starts at puberty with a peak incidence at 40 years of age and is more common in males. Patients develop symmetrical, well demarcated, dull or yellowish red patches and plaques with overlying adherent, yellowish greasy scales. Seborrhoeic dermatitis has a distinctive distribution in areas rich in sebaceous glands. Patients presenting with sudden onset severe seborrhoeic dermatitis should be screened for risk factors for HIV.