I explicitly said hair dye won’t do that, but that chemicals can impact your scalp permanently, i.e. chemotherapy or radiation. Acne can impact your scalp perm

I explicitly said hair dye won’t do that, but that chemicals can impact your scalp permanently, i.e. chemotherapy or radiation. Acne can impact your scalp permanently (scar tissue from acne can prevent new growth in those areas). Using too many extensions (particularly if sewn into the scalp) can damage your scalp permanently (again, scar tissue). Having said that, over the counter stuff absolutely affects the the health of your hair and dying too frequently, leaving dye on too long, using a poor quality of dye (of which over the counter almost always is), too much peroxide (which is often needed so the color can stick) can absolutely damage the hair on your head permanently (until that hair is cut off and regrows). The only way to truly recover from the damage due to hair dye is to cut it all off and regrow, which for people with long hair, can take a tremendous amount of time.