Actually, That's Not Dandruff (and Here's What to Do About It)
Dandruff occurs on your scalp. So, too, does a skin condition called seborrheic dermatitis, which could show up on your scalp, as well as on your ears, the middle of your face and/or your upper chest, says Ronda Farah, MD, assistant professor in the department of dermatology at the University of Minnesota. The skin disease looks more scaly and inflamed than dandruff; however, "both are itchy and cause flaking—and the treatment for both dandruff and seborrheic dermatitis is the same," she says. Though researchers are still uncertain about what causes seborrheic dermatitis, the condition may develop due to the yeast that naturally resides on skin, to weather conditions and/or to stress. Farah recommends patients alternate each day using either a zinc pyrithione shampoo or a selenium sulfide shampoo. (Both antidandruff shampoos are available over-the-counter.) Rotating between the two may be a better way to keep the yeast on your scalp from overgrowing, she says. To treat related facial symptoms, a dermatologist or primary care doctor may recommend a topical antifungal or topical steroid to alleviate rashes.
You're reacting to your hair oil
Even your go-to shampoo may be to blame. "People will say, 'Oh, I've used this for my whole adult life, I can't be allergic to it,' but that's not true. You can become sensitized to a hair product and develop what is called a contact allergy," says Lindsey Bordone, MD, a dermatologist at ColumbiaDoctors Midtown and an assistant professor of dermatology at Columbia University Medical Center. Along with scalp flaking and redness, you may also notice a rash on other parts of your body where the product touched your skin, such as on your neck or eyelid, says Bordone. The essential oils in 'all-natural' hair products can also irritate the scalp, as can some ingredients in hair-regrowth treatments. After you stop using the offending product, things should start to clear up in two to three days, though more severe reactions can take up to two weeks to go away, says Farah. Most often, though, the culprit of contact allergies is hair dye, specifically a commonly used chemical called PPD (paraphenylenediamine). If you experience this and are not considering the idea of going gray, there are coloring alternatives out there—ask your hairstylist.
It's a patch you didn't know to look for
Dandruff is flakiness that happens all over the scalp, while flakiness in a targeted area may be a sign of something more. So, if a patient has a new quarter-size area on her scalp that always flakes, Farah may consider skin cancer as a cause. "Skin cancer on the scalp is not rare. I see patients with skin cancer of the scalp multiple times per week," says Farah. Other signs may include that the spot won't heal, bleeds or is painful. As you age and your hair thins at the crown, you're at an increased risk for skin cancer in this area. Farah suggests asking your stylists to notify you if they see any spots on your scalp. (They've been known to find them.) And if you see something on your own, it's important to bring it up with your doctor. While there are many different types of skin cancer, studies show melanoma can be especially dangerous when located on the scalp.
It's the tip of a full-body issue
The scalp is also just another place where autoimmune conditions may show up—and, sometimes, that may be the only place you find such a clue, says Farah. These diseases occur when your immune system attacks healthy cells and organs in your body; psoriasis, for example, is commonly marked by an itchy, scaly rash, which can affect the scalp. Of course, if you see flaking, you don't have to assume you have an autoimmune condition if you're otherwise healthy. As long as you're not dealing with unexplained symptoms (fatigue, muscle aches and a low fever are often the initial signs of an autoimmune disease), it's okay to try using regular treatments like antidandruff shampoos for four to six weeks. If the rash doesn't start clearing up then, see your doctor (or dermatologist). A biopsy may be the first step to discovering what's really going on.
Your pet passed it on
Fungal infections like ringworm can infect the scalp, but—deep breath— these types of scalp infections are unlikely in adults. "We get this question from patients all the time, but thankfully, in the U.S., this is rare," says Farah. However, the infection can show up in children. One study in the journal Pediatrics found that nearly seven percent of school-age children in one metropolitan area tested positive for the fungus that leads to ringworm. You can catch ringworm from an infected cat or dog. Using a comb or phone carrying the infection can also transfer the skin infection to you. In the event you (or your kids) were potentially exposed to ringworm and you have flakiness in one area of your scalp that leads to hair loss, get checked out by your doctor, who can test for it.