I don't know. I remember when I first got on this forum this was a huge pt of interest, not with Ghostbond in specific, but adhesives in general.
If you want to have hair by way of wearing a hairpiece, you have to assume certain nuissances. Removing, cleaning, re-installing. You have to be gentle with the hair, and be modest in the way you wash it, etc.
Some people don't wear sunscreen because of "all the chemicals." Who really knows. I know I don't immediately react to ghostbond the way I do to acrlyic based products, like certain clear glues & tapes.
I think given the the totality of dangers most people are faced with daily, adhesive on the head should be a low priority worry...