I didn't love this on the face simply because it was a little too gentle for me (i can go harsh with acids, retinol (separate nights from acids), and vitamin c with rarely any problems.) But, when trying to decide what to do with the rest of what i bought i decided to try it on my scalp, given i have had chronic dandruff since i age 7, and BHA is sometimes used for that.
I shampoo with my usual dandruff shampoo (active is zinc), rinse, then apply a fair amount of this exfoliant directly on the scalp. Leave it in for a few minutes while doing other shower stuff, then rinse quickly with water (if you don't rinse at all it kinda makes your roots feel like they have been hairsprayed.) Its really reduced the visible amout of dead skin coming off in the day after a shower!
The funny thing is, i noticed that if i use this, I don't have to use conditioner after to avoid my hair being tangled! I suspect this has to do with shampoo being basic in Ph and that raising the hair cuticle makes it tangle easier, and this being an acid helps reset and smooth things.
I will say, I've got kinda wavy but mostly straight hair that doesn't need a lot of outside moisture, and up until now i really only needed conditioners for tangle reduction, so ymmv. But, I'm very happy with how this has helped my scalp and simplified my routine in the year+ since i first used it in this fashion. I just placed an order to majorly stock up because its a staple now!