A new study suggests that counting the hairs lost after 60 seconds of combing or brushing is a reliable method for assessing hair loss.
"Currently, there is no widely accepted or standard method for assessing the number of hairs shed daily," write researcher Carina A. Wasko, MD, of Baylor College of Medicine in Houston and colleagues in the Archives of Dermatology.
Researchers say the commonly held belief that it's normal to shed up to 100 hairs a day is based on the assumption that the average scalp contains 100,000 hairs. Although this idea is widely held, researchers say it has not been proven scientifically to be an accurate measure of normal vs. problem hair loss in men or women.
It also does not account for whether shedding remains constant with age or if normal hair loss rates are comparable among men and women.
In the study, researchers examined hair loss in 60 healthy men with no signs of male pattern baldness. Half were between the ages of 20 and 40 and the other half between ages 41 and 60.
Each of the men was given identical combs and instructed to wash their hair with the same brand of shampoo for three consecutive mornings. On the fourth, fifth, and sixth mornings, they were asked to comb hair forward over a towel or pillowcase of contrasting color for 60 seconds before shampooing and count the hairs shed.
The results showed younger men shed an average of 10.2 per 60-second test and the older men shed an average of 10.3 hairs per test.
"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," write the researchers.
Researchers say that low variability between tests over time and across age groups suggests that the 60-second hair count is a simple and practical tool for assessing normal vs. problem hair loss in men.
They say the next steps are to verify the test in women and in people with male pattern baldness and other forms of problem hair loss to determine hair count measures.