I have had a lot of dandruff too, also behind my ears and on my eyebrows and forehead. And as I know it is in most cases caused by some fungus naturally on the scalp but when there's too much of it, but it can be caused by any other factors such as bacterias, dry skin and dehydration, etc.
I personally used (and use now as well) hair masks, in which I add sodium bicarbonate (it is also named baking soda). And I try to make masks mostly natural. There are a lot of ingredients you can put in a hair mask such as apple cider vinegar (which regenerates your skin) or any type of oil (which softens your scalp), and many more. How baking soda actually works on your scalp is not only exfoliates it but fights specific types of bacterias and fungis, balancing the amount they can be found on your scalp, and exfoliates your skin.
If you have severe dandruff don't use baking soda at first, but for beginning opt for a softer home made treatment such as an egg blended with garlic (I know this worked for a friend of mine, but everyone is different), or apple cider vinegar alone or with other natural ingredients that may help, because the fact is, baking soda can be harmful for way too damaged skin, like mine was. I could literally scratch my scalp a bit and it'd be bleeding, but for normal dandruff baking soda combinded with any ingredient above may work just fine.
Other benefits of baking soda on the skin are: removes bad smell (I use a paste made of baking soda and a bit of water as a natural deodorant), removes dead skin and exfoliates (add it in shower gel or make a scrub adding rose or lavander water, or any water of your choice), leaves the skin soft after any aplication.
I hope I helped some people with theese
just find what works for you