Telogen effluvium is asymptomatic. Hair loss in telogen effluvium is evenly distributed throughout the scalp. Approximately 30% to 50% of the scalp hair is involved, so patients do retain a fairly full head of hair even during the worst of the shedding process (Fig. 76-1). There is no scarring. Sometimes referred to as telogen defluvium, the condition is a sudden diffuse loss of scalp hair occurring 3 to 6 months after a stressful event, such as systemic illness or pregnancy. The hair loss is caused by the simultaneous cycling of an unusually high percentage of scalp hairs into the resting, or telogen, phase. Normally, approximately 5% to 10% of hairs are in the telogen phase; during telogen effluvium, this number increases to approximately 30%. Normally, resting hairs are retained in the scalp for approximately 80 to 100 days until they are shed. This explains the 3- to 6-month delay in the development of clinically apparent hair loss after the stressful event. Additional causes of telogen effluvium include neoplasms, infections, and crash diets. Some medications have also been implicated, including heparin, coumarin, propanolol, haloperidol, and lithium.