"Currently, there is no widely accepted or standard method for assessing the number of hairs shed daily," according to background information in the article. The widely held belief that it is normal to shed 100 hairs per day is based on the assumption that the average scalp contains 100,000 hairs, 10 percent of which are in the telogen (resting) phase. Although this idea is prevalent, it has not been scientifically validated and does not indicate whether shedding remains constant with age or if it is similar between men and women.

Carina A. Wasko, M.D., of Baylor College of Medicine, Houston, and colleagues studied hair loss in 60 healthy men (half age 20 to 40 and half age 41 to 60) without evidence of alopecia (baldness). All participants were given identical combs and instructions to wash hair with the same brand of shampoo for three consecutive mornings. On the fourth day, they were asked to comb hair forward for 60 seconds over a towel or pillowcase of contrasting color before shampooing. The men combed their hair this way and then counted hairs shed for three consecutive days. This procedure was repeated in eligible participants six months later.

Participants age 20 through 40 shed 0 to 78 hairs, with an average loss of 10.2 hairs per 60-second test. Men age 41 to 60 shed 0 to 43 hairs, with an average loss of 10.3 hairs per 60-second test. Results were consistent on consecutive days for all participants. "When repeated six months later in both age groups, the hair counts did not change much. The hair counts were repeated and verified by a trained investigator, with results similar to those of subject hair counts," the authors write.

"In summary, the 60-second hair count is a simple, practical and objective tool for monitoring conditions associated with hair shedding," the authors conclude. "Low intrapatient variability demonstrates that dependable results over an extended period of time are obtainable. The similarity between investigator and subject hair counts indicates that patients can reliably count hairs.

"Studies of the 60-second hair count in normal women and in the setting of hair disease still need to be performed."

Co-author Dr. Miller is a consultant for and has received honoraria from Pfizer Inc. This study was supported by a study grant from Merck.