Bilberry for dandruff.
Green hairdressers gave me some natural haircare hints.
I taught a group of ecological hairdressers about herbs for haircare (concentrating on internal use - they were well versed in external uses). And they told me things. Like this one:
A mash of fresh bilberries (Vaccinium myrtillus) put as is on dandruffy hair and left on for, say, half an hour, regularly for a week or two every day, will cure dandruff.
It won't color light hair blue (or red, or green - take your pick) either, unless the hair is bleached or otherwise tampered with.
I have no idea why this works, but they said it's very effective. It's also easy to make up here in Finland, where everybody and their uncles, grandmas, aunts, grandads, sisters, parents, children, cousins, etc. (... you get the picture) go pick bilberries by the bucketfuls every year.
Honest. 100 liters of bilberries picked in late summer isn't even rare, and that's not counting any of the other berries.
Another dandruff cure, for those less blessed in the berry department, is bicarbonate of soda. Use a handful of the soda instead of shampoo, wash, and rinse. Use just this as a shampoo for 2-3 weeks, no normal shampoo at all.
Diluted vinegars also work as dandruff shampoos. One favorite is rosemary vinegar, another is peppermint vinegar.
I don't know why both acids and basics work, either. Do look into the reason for the dandruff as well: stress, diet, fungi?