Many people have started to pay closer attention to the ingredients in their skin and hair care products, thanks, in part, to the clean beauty movement. One particular ingredient, DMDM hydantoin, has attracted plenty of negative attention.

DMDM hydantoin, a white, odorless preservative, commonly appears in shampoos, conditioners, styling products, moisturizers, and even foundation makeup, says Enrizza Factor, MD, a board certified dermatologist and owner of EPF Dermatology Skin Therapy.

This preservative does help prevent products from spoiling. But it’s also a common allergen that’s raised concerns in recent years. Class-action lawsuits against cosmetics companies have even suggested it may trigger hair loss.

Below, get the details on how DMDM hydantoin works and what research says about its potential risks.

The main benefits of DMDM hydantoin lie in its antimicrobial properties.

In basic terms, this means it can help prevent the growth of mold and other fungi, yeast, and harmful bacteria, Factor says. As a result, products that contain this ingredient might remain fresher (and safer to use) for longer periods of time.

Preservatives like DMDM hydantoin play an especially important role in products you keep in your shower — think shampoo, conditioner, and body wash — since the warm, humid conditions can encourage bacteria to grow.

DMDM hydantoin has come under fire in recent years, mainly because it releases small amounts of formaldehyde. This chemical helps prevent your products from going bad, but at high doses, it may have the potential to cause cancer in humans.

Potential safety concerns include the following.

Allergic reactions

DMDM hydantoin is a known skin allergen.

A 2011 study suggested this allergy isn’t uncommon. People who most commonly experience a reaction include women with chronic dermatitis and workers who come in frequent contact with products that release formaldehyde.

A 2010 review suggested that formaldehyde-releasing products are more likely to cause contact skin irritation in people with pre-existing formaldehyde allergies.

Allergic reactions to cosmetics typically appear as contact dermatitis, or an itchy rash that involves discolored patches of skin. You might also notice:

Cancer

The National Toxicology Program classifies formaldehyde as a known carcinogen, since evidence from human studies have suggested that exposure to the chemical may raise your risk of developing at least one type of cancer.

According to the National Cancer Institute, people who are exposed to formaldehyde through their daily jobs have a much higher risk of developing cancer than the general population. For example:

  • embalmers
  • carpenters
  • medical technicians
  • textile or metal industry workers

Keep in mind, though, that formaldehyde exposure from DMDM hydantoin is minimal, as Factor emphasizes. To put it into perspective, Factor compares the amount of formaldehyde released from these products to the amount naturally occurring in an apple or pear.

The American Cancer Society notes that few human studies have explored the potential cancer-causing effects of formaldehyde in small doses.

As noted above, experts have found links between more frequent exposure to formaldehyde, or exposure to larger amounts of formaldehyde, and cancer risk.

People who work with formaldehyde may have a higher risk of:

  • leukemia
  • cancer of the sinuses
  • cancer of the throat

Existing research doesn’t suggest the low amount of formaldehyde released by skin care products with DMDM hydantoin can cause cancer, but future research may offer more information about its potential effects.

Keep in mind that, if you work in a salon and frequently use hair and beauty products containing DMDM hydantoin, you may be exposed to more formaldehyde than someone using these products less often.

That’s why you’ll always want to follow recommended safety practices, like working in a well-ventilated area and wearing protective gloves and face coverings.

Hair loss or damage

Recent class-action lawsuits have alleged that DMDM hydantoin causes hair loss, but no scientific research supports this.

Shampoo generally doesn’t cause hair loss. That said, severe scalp irritation that develops after an allergic reaction can sometimes lead to hair loss.

“DMDM hydantoin is safe as a cosmetic ingredient at current normal levels of use in products,” says Factor.

A 2013 safety assessment concluded that formaldehyde may be used safely in cosmetics “if established limits are not exceeded.”

According to the Cosmetic Ingredient Review, an independent panel of expert physicians and toxicologists, DMDM hydantoin is safe at levels of 0.074 percent or less. Cosmetic products typically won’t exceed that limit, according to older research from 1988.

As recently as 2015, the United States and the European Union allow cosmetic and household products to contain up to 0.2 percent of free formaldehyde and up to 0.6 percent of formaldehyde releasers like DMDM hydantoin.

Experts emphasize, though, that even this low concentration could still prompt a skin reaction in people allergic to formaldehyde.

Factor recommends connecting with a healthcare professional or dermatologist if you believe any skin care product has triggered symptoms of an allergic reaction, such as:

  • skin discoloration or redness
  • itchiness
  • swelling
  • hives

Dermatologists can conduct a patch test, which involves placing a very small concentration of common allergens on your skin. After 48 hours, they’ll remove the patches over each allergen sample to determine which ingredients led to the reaction.

Once you’ve found those allergy triggering ingredients, you’ll want to check the labels on all your skin and hair care products, so you can make sure to avoid them in the future.

You may also want to avoid products with DMDM hydantoin, or at least limit your use, if you live with chronic dermatitis or have sensitive skin.

Still on the fence about whether or not to try a new product?

It never hurts to scan the label in the Environmental Working Group’s Healthy Living app to check how it rates according to the organization’s rigorous standards for health and safety.

DMDM hydantoin is a common preservative that extends the shelf life of beauty and skin care products. But since it releases small amounts of formaldehyde, a reported carcinogen, its use has raised some concerns.

While current findings suggest it takes long-term exposure to higher doses of this chemical to increase health risks, it can’t hurt to avoid products with DMDM hydantoin if you’re allergic to formaldehyde or prone to dermatitis.

If you experience hair loss, rashes, or any other symptoms of irritation that seem linked to product use, a good next step involves connecting with a dermatologist to narrow down the cause of these reactions.

Rebecca Strong is a Boston-based freelance writer covering health and wellness, fitness, food, lifestyle, and beauty. Her work has also appeared in Insider, Bustle, StyleCaster, Eat This Not That, AskMen, and Elite Daily.