I know hair dyes can be bad for your hair but if you do it which is safer for scalp and hair, store bought or salon. what's your opinion. ty?

Well: Can't say depends on the specific product each one is different chemicals doesn't matter if it's store-bought or from the beauty.It's not where you buy the chemicals in it that cause the problems

It is hard to tell : The difference between store vs salon bought hair dye products without knowing the ingredients. Certainly, there are products claim they use more natural/less harmful ingredients but often hard to verify. Comparing scalp and hair, it is less harmful to apply only to Hair,already dead tissue, as scalp is like cutaneous barrier and can potentially absorb those chemical/toxin.