But what exactly is dandruff? And how is it different from a dry scalp? We spoke to Dr. Jennifer MacGregor of Union Square Laser Dermatology in New York City to get to the root of the issue (pun most definitely intended). 

So What Is Dandruff?

Dandruff is essentially the flaking of the scalp, and when we refer to dandruff, we’re usually talking about a common skin condition called seborrheic dermatitis, MacGregor explained. Recent research suggests dandruff and seborrheic dermatitis are “of a continuous spectrum of the same disease,” but while dandruff is just on the scalp, seborrheic dermatitis can occur on other parts of the body, too. 

“The typical mild cases look like flaky or scaly patches and sometimes have underlying redness,” MacGregor said, noting seborrheic dermatitis is typically found on the scalp, behind the ears, and around the eyebrows and nostrils. It may appear on the whole face and chest. 

Seborrheic dermatitis is “very common,” MacGregor said. According to a study in the Journal of Clinical and Investigative Dermatology, its estimated that the condition and dandruff combined “affect half of the adult population.”

The exact cause of seborrheic dermatitis is unknown, but according to the Mayo Clinic, it might be related to a yeast called malassezia that is found in the oil secretions on the skin, or it could be an irregular response of the immune system. The condition often worsens in those living with Parkinson’s disease or HIV. 

What About Dry Scalp?

A dry scalp, on the other hand, is a form of dry skin, and “there can be scaling and itching with this condition as well,” MacGregor explained. 

Dry skin also tends to get worse with age and can be hereditary, MacGregor said. While it’s possible to have dry skin that isn’t part of another condition, it’s often associated with eczema, a non-contagious dry skin condition that commonly presents itself in rough or scaly patches on the skin. Severity of eczema symptoms vary from person to person. 

How Do You Tell The Difference?

As MacGregor explained, “mild cases of both dry scalp and dandruff can look and behave exactly the same way,” so in order to properly treat either condition, you need a proper diagnosis. 

“If you have mild scaling in the scalp or on the skin, you might not know what is the cause unless you are carefully examined by an expert,” MacGregor said. “For redness and scaling, or if symptoms persist despite good skincare, consult an expert for evaluation and possible prescription of stronger topical anti-inflammatories for flares.”

How Can You Prevent Them?

Well, according to MacGregor, you should start with a gentle skin care routine of showering with warm (not hot) water and applying moisturizer to the face and body within two minutes of bathing. 

MacGregor said seborrheic dermatitis can’t completely be prevented, but if you’re sure you have the condition, you can use medicated shampoos from Selsun Blue or Head and Shoulders that contain selenium sulfide or zinc pyrithione (substances that reduce flaking and irritation) or Nizoral, which contains ketoconazole (an antifungal). She suggests keeping the product on your hair in the shower for five minutes and using it three times a week to help maintain a clear scalp and prevent recurrences. For more severe cases, doctors may prescribe anti-inflammatory medications. 

Those with dry skin or eczema should use barrier ointments or creams, which help protect the skin from excess moisture, for the worst areas and a moisturizer with ceramides twice daily. For very dry skin, MacGregor suggests adding Vaseline to moisturizer for more barrier protection.

For the scalp specifically, choose moisturizing shampoos and conditioners, which MacGregor explained usually have less soap or detergents in favor of more hydrating ingredients like oils.