How Does Dandruff Shampoo Actually Work?

Head flakes aren’t as unique as snowflakes, but they’re closer than you think.


It’s always a relief when your anti-dandruff shampoo magically whisks away those little skin flakes. But have you ever wondered how the clean-up gets done? It’s more complicated than just sweeping up your scalp.

The first reason is that dandruff can be caused by a variety of things. It could be genetic; your head could be irritated by a hair product you’re using, and your scalp is shedding its upper layer of skin to protect itself; your skin could be too dry, or conversely, it could be producing too much sebum (the oil it uses to keep itself moisturized), allowing your scalp to become a buffet/breeding ground for the fungus Malassezia.

“There are multiple active ingredients in shampoos that work against dandruff,” says dermatologist Rajani Katta. “The active ingredients work via different mechanisms of action.” That is to say, different dandruff shampoos target different aspects of the problem, and all are effective in their own way. Per the Mayo Clinic, there are five major ingredients used in dandruff shampoos:

Salicylic Acid
This clever substance works by gently breaking down the outermost layer of skin on the scalp, helping prevent skin cells from clumping up and turning into flakes. This has the dual effect of making them harder for other people to see, and easier for you to wash away. It also helps moisturize your scalp, so it’s less prone to drying out in the first place. (Fun fact: It’s the ingredient you’ll find in our very own anti-dandruff shampoos.)

Pyrithione Zinc
This ingredient targets some of the potential causes of dandruff, killing bacteria and fungi like Malassezia.

Tar (yes, really!)
It might sound like an odd substance to rub into your head, but it reduces flaking by slowing down the death of your skin cells. It can, however, cause skin irritation and inflammation in some people.

Selenium Sulfide
Another antifungal ingredient, this specifically targets Malassezia by slowing down your sebum production and drying out your scalp.

This also works to slow the growth of the fungus that can cause dandruff. Shampoos containing this ingredient are too powerful to be sold over the counter, however, so doctors will prescribe them for people with very severe fungal infections.

We’re obviously fans of our Anti-Dandruff Shampoo (wouldn’t it be weird if we weren’t?) but each ingredient has its uses. “It depends on the individual,” says Katta. “I’ve seen some people respond really well to one active ingredient, and sometimes they’ll respond really well to another.” If you’re unsure which one is right for you, go see your dermatologist to figure out what you need to get rid of the flakes. After all, the important thing isn’t how dandruff shampoo works, but that it works for you.