The "wash test" involves washing one's hair over a sink five days after the last shampoo, a waiting period some might find objectionable.
A more up-to-date method is the 60-second hair count, used in this study.
Sixty healthy men aged 20 to 60 without evidence of baldness participated. All were white and all but one had straight hair. (The authors excluded, for the most part, men with curly hair and long hair "because of the difficulty of running a comb through the hair, which would lead to increased numbers of broken" hairs, which weren't counted.)
The men washed their hair three mornings in a row with Neutrogena T/Sal shampoo. On the fourth day, they were issued identical combs and instructed to comb their hair forward over a towel or pillowcase of contrasting color. They were then asked to count the hairs that had dropped out. This comb-and-count procedure was repeated on the next two days and the number of hairs was validated under a microscope.
After six months, the participants repeated the full procedure.
Based on these results, the authors concluded that losing 10 hairs is "normal." In younger men (aged 20 to 40), the shedding range was 0 to 78 hairs with a mean of 10.2 hairs. In the older men, the range was 0 to 43 hairs with a mean of 10.3 hairs.
Here are instructions on how to perform the count:
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