Does Selenium Sulfide Cause Hair Loss? We Asked the Experts

If you've ever dealt with dandruff, you've likely used, or at least heard of, selenium sulfide. It's a popular active ingredient in many flake-fighting shampoos, helping to address various symptoms associated with dandruff. And that's all fine and dandy, but experts point out that it's important to keep in mind that improper or overuse of selenium sulfide can paradoxically end up having some detrimental effects on both your hair and scalp. Ahead, we spoke to the three experts who weighed in on what you need to know before you start using selenium sulfide.

What Is Selenium Sulfide?

"Selenium sulfide is an agent that treats dandruff and other fungal infections of both the scalp and skin," explains Hill. While there are multiple factors at play regarding dandruff, an overgrowth of a yeast known as Malassezia is a primary culprit. Selenium sulfide is both an anti-fungal that slows the growth of this yeast while also relieving the inflammatory side effects associated with dandruff, says Yates. To that point...

Benefits of Selenium Sulfide

Yes, selenium sulfide is a great anti-fungal active ingredient, but it also offers some additional benefits. "It reduces flaking, as well as itching, irritation, and redness of the scalp," points out Reavey, noting that this is also why it's often used to treat other scalp conditions, such as seborrheic dermatitis.

Can Selenium Sulfide Cause Hair Loss?

It's not clear-cut, unfortunately. "There have been some hair loss side effects reported when using selenium sulfide, but there is no evidence that it's the single causing factor," explains Reavey. As a general rule of thumb, any hair loss is typically a result of multiple factors. At the same time, selenium sulfide may play a role and exacerbate the condition; it's not likely that it's the root of the issue (pun intended.) "If you're using selenium sulfide, it's usually because you're treating a scalp condition, which is caused by poor scalp health, diet, hormones, illness, stress, and/or irritation to products," says Reavey. In short, there are already problems happening with your scalp that can be contributing to hair loss.

Hill also notes that many of the benefits of selenium sulfide can actually be a positive thing in managing hair loss. "It helps reduce inflammation, which is harmful to the hair follicle and depletes it of necessary nutrients, and also controls both excess yeast and oil from pooling on the scalp, which can lead to hair shedding and loss," she says. (Though all of this only applies if you actually do have dandruff or a fungal scalp infection.)

Still, she and the other experts we spoke with are quick to note that incorrect or overuse can, in fact, be detrimental to healthy hair and scalp function (more on the right way to use it in a moment). For example, the downside of using selenium sulfide is that it can lead to excessive dryness of the scalp, which in turn ups the likelihood of hair breakage, one form of hair loss, says Yates. "Think of it as a branch on a tree becoming dried out. Any mechanical disturbance of that area will cause the branch to break. Similarly, if there's a lack of hydration or lubrication along the external hair shaft, any mechanical disruption will cause the hair to break," he explains.

And if you're using selenium sulfide just for kicks and giggles, you can really run into some issues.
"Selenium sulfide can irritate, inflame and dehydrate the skin on the scalp that does not have outbreaks of dandruff. This can disrupt regular scalp and hair follicle function," says Hill, another potential contributing factor to eventual hair loss.

How to Use Selenium Sulfide

For starters, only use selenium sulfide if you have a scalp condition, like dandruff, and even then, it should by no means be a regular player in your haircare routine. "Use it episodically," recommends Yates. "While you won't see improvement after just one use, you should see results after about a week or so." Then, once the condition is better, stop using it. "Your scalp has a microbiome, just like your gut, and continued use of ingredients such as selenium sulfide will disrupt this and can end up making the condition you're trying to treat worse," points out Reavey.

While the percentages of selenium sulfide found in shampoos are formulated to be safe for the hair, remember that this is an ingredient that's still meant for the scalp. As such, Hill encourages application directly to the scalp (ideally with a bottle that has an applicator that touches the scalp directly) and only on areas where you have actual dandruff. In between uses, supplement with a hydrating shampoo and conditioner. Yates says ingredients such as biotin, yucca root extract, and pumpkin seed oil are all good to seek out.

Oh, and FYI, selenium sulfide reacts with and can leave a black tarnish on silver, so make sure to take off any silver jewelry before washing your hair with one of these shampoos, says Yates.

How Often Should You Use Selenium Sulfide?

You should only use selenium sulfide around twice a week. Remember, excess use can cause more harm than good. Once you start to see your original issues (e.g. dandruff) subside, start weaning your use to once a week. After that, only use it if you notice any flare ups.

Side Effects

Along with the aforementioned potential for irritation, it bears mentioning some health and safety concerns around selenium sulfide in general. "The Environmental Working Group rates selenium sulfide at an eight, which shows concerns for its toxicity to the body and the environment," notes Reavey. Yates adds that it's actually banned in both the EU and Japan for this very reason.

At the end of the day, if you have dandruff, you can try other active ingredients. However, if you do want to use selenium sulfide—because it is undoubtedly an effective solution—make sure to only do so for limited amounts of time to maintain the health of both your scalp and hair.