Is it true that vellus hairs on any given area of scalp are relatively normal for a healthy scalp?

Question

And is the ratio cut of 20 percent for this? So meaning in a healhty scalp at any given area it's normal to have 20 percent of "vellus" hairs for male and female? Do these vellus hair grow on scalp like peach fuzz because they can grow like it grows on the face?

Jeff Donovan, MD, PhD · Answer

This a very crude cut off for diagnosing AGA but no one does not “normally “ find 20 % everywhere. Normally it’s closer to 10 % but the cut off of 20 % variation of hair diameter was set to make things easy for people.

In 2009, Rakowska et al. proposed 3 major and 3 minor diagnostic dermoscopic with a high specificity to diagnose AGA.

The major criteria were : more than four yellow dots in four fields decreased average shaft thickness and more than 10% of thin hairs (;0.03 mm) in the frontal area.

You can see the cut off here was 10 %

The more accurate the methods one uses to evaluate androgenetic alopecia the lower the cut off can be.

20 % is a cut off that is very generous and unfortunately if we all stick with that we will miss properly diagnosing alot of early staged AGA.

Is it true that vellus hairs on any given area of scalp are relatively normal for a healthy scalp?

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