This happened to me as well one time years ago.
I cut a sample of hair during this time just to prove that it was not in my imagination and to also show it to people who made my hair pieces so they could figure out what colors to use.
If you have hair growing back and intend to keep it, then start brushing it as a regular habit and be sure to brush it before washing it. Be gentle with it since the roots are probably quite fragile.
Also, there is a list of herbal remedies that can work to keep you from loosing hair.
I would also ask your dermatologist if they have any treatments to keep you from losing it again.
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