Dandruff and Seborrheic Dermatitis: A Head Scratcher 400 higher shampoo frequencies and the availability of effective over- the-counter and prescription antidandruff shampoos in the United States, the most recent prevalence study shows dandruff is occurring at a much higher rate and severity in the United States than in China.5 The higher prevalence of dandruff in the United States is most likely associated with a lower use of antidandruff products (10‑20%) than in China (40‑52%). Table 1. Adherent scalp flaking severity scores in adults and teens in the United States and China Category by Creed/Gender Adults Teens African American Females 29.3 27.1 African American Males 23.4 26.0 Caucasian Females 22.7 22.8 Caucasian Males 21.3 23.7 Chinese Females 12.1 12.4 Chinese Males 13.6 11.2 Pathology The visible symptoms of dandruff and seborrheic dermatitis, superficial flaking and redness, are manifestations of abnormal epidermal structure and function.56 Flakes are generally believed to occur in “patches” on the scalp and that these lesions randomly “move” about the scalp over time. However, the underlying stratum corneum irregularities occur throughout the scalp of affected individuals,56 suggesting the actual flakes are the end result of a cycle of skin distress that may or may not be visible to the unaided eye. The stratum corneum of dandruff-affected individuals shows striking features consistent with a hyperproliferative state, which is supported by functional studies that measure accelerated epidermal maturation times.51 The physical features accompanying hyperproliferation are dramatic.6,53 An electron microscopic study of stratum corneum56 revealed that dandruff-affected stratum corneum exhibits parakeratotic nuclei, lipid droplets within corneocytes, a