It’s an embarrassing skin condition that’s much more common than you might think — and one that’s remained somewhat a mystery to scientists for centuries.

I’m talking, of course, about dandruff: the sometimes itchy, always annoying medical condition that causes white flakes of dead skin cells to rain down from our scalp with alarming speed. But what exactly is dandruff, what causes it, and how do we treat it? Let’s take a brief look.

An Imbalance

At its simplest, dandruff is what happens when our scalp sheds more skin cells than it normally should. In more severe cases, the skin atop the scalp changes in consistency and becomes scaly and possibly irritated. This makes the shed skin cells clump together, and the flakes more noticeable and plentiful.

A whopping fifty percent of the population worldwide is believed to have dandruff at any given time, and there’s some indication that rates have been climbing over time. But the question of why dandruff happens in the first place isn’t easily answered.

For instance, we know that dandruff is more likely to happen during adolescence, suggesting that the higher production of sebum (an oily secretion that lubricates and waterproofs our skin) is a contributing factor. But people with dandruff are actually more likely to have especially dry scalp skin.

Elsewhere, scientists have long pointed the finger at a type of yeast called malassezia as a likely culprit. While malassezia is typically a harmless part of the community of microbes that envelopes our body, people with dandruff are known to have much higher amounts of the yeast on their scalp. More recently, though, some researchers have implicated other bacterial microbes like Propionibacterium and Staphylococcus. Others have speculated that the overabundance of malassezia isn’t really what’s causing dandruff, they’re just coincidentally getting fat off the excess production of dead skin cells. Dandruff can also sometimes be seen as an offshoot of preexisting skin conditions like psoriasis, though scalp psoriasis is considered more serious and longer-lasting.

At the end of the day, an individual case of dandruff can be caused by more than one thing, so long as it throws the tenuous balance of our scalp’s health into disarray.

What To Do

Thankfully, while there’s still a lot we don’t understand about dandruff, there is plenty more we know about how to treat it.

For cases of mild dandruff, simply remembering to shower regularly can prevent oil and skin-cell buildup. And for more severe cases, there’s any number of specialized shampoos that can trim down the bacteria and fungi living on our head. These shampoos will require trial and error to get right, as some won’t work for a particular person, while others may only work for a brief time. Keeping your scalp away from hair care products that irritate the skin or using ones that allow our skin cells to live longer than usual can also help reduce flakiness. For those brave enough, you could also try shaving your head completely — dandruff isn't impossible to have if you're bald, but it is much less likely.

Should you have an especially bad bout of dandruff, though, it’s probably for the best that you visit your local doctor or dermatologist.