Combination of the words 'sandwich' and 'dandruff' referring to the tiny crumbs which litter your clothes after eating a sandwich and give the impression that you are suffering with a dry scalp.
"Don't look at me like that - I'm not suffering from a dry scalp it's just sandruff"
The phenomenon of sand falling out of your hair after spending a lot of time on the beach. If one is wearing a dark shirt, it can appear that they have heavy dandruff.
After four days on the beach, my suit was collecting sandruff every time I scratched my head.
