Dandruff is something half of the people in the world deal with, yet I cannot seem to find any good translation for it, nor come up with a word for it myself.
I found the word "kaphaŭteroj" here, which seems to me like a good translation.
John Well’s dictionary suggests (har)skvametoj. It also appears as the third definition of the word skvamo in PIV:
3 ⚕ Ĉiu el la epidermaj lamenetoj, kiuj disiĝas de la haŭto, speciale de la kapa.
It does seem kind of an odd word though seeing as it normally refers to scales of a reptile. Personally I think Robin’s word is good too. Incidentally, that word is also backed up by PIV:
haŭtero. Skvameto, kiu defalas de la haŭto, precipe de la kapo.
In the Tekstaro I found no hits for skvamet. There were 30 hits for skvam but none of them seem to refer to dandruff. There were no hits for haŭter either.