Here's What Dermatologists Think About "Bad" Hair Ingredients

haircare ingredients on pink background


In both skincare and haircare there is one golden rule: ingredients matter. When selecting products, it's important to understand what makes them beneficial or harmful to your hair. But since there are so many terms that get used when it comes to hair products—like clean, fragrance-free, and sulfate-free—it can feel overwhelming to try and understand them all. Is fragrance really even bad for your hair? Is sulfate-free really better?

In the age of the influencer, it only takes one negative review for an ingredient or product to be baselessly written off (and for brands to adjust their marketing jargon accordingly). But we have to keep in mind that for certain ingredients, the very reason they don't work for one hair type is what makes them so successful for another.

Don't get us wrong —there are certainly some shifty ingredients out there that deserve their reputation. But after conducting thorough research and interviewing two board-certified dermatologists and a trichologist, we've discovered that a lot of "bad" haircare ingredients actually have a rightful place in certain formulations.

Ahead, discover what our experts actually think about notoriously "bad" haircare ingredients, from formaldehyde, to sulfates, to parabens, and beyond.

Meet the Expert

  •  Dr. Deanne Mraz Robinson is a board-certified dermatologist based out of Modern Dermatology in Westport, CT.
  • Gretchen Freise is a BosleyMD certified trichologist specializing in hair and scalp health.
  • Dr. Orit Markowitz is a Board-Certified Dermatologist and Founder of OptiSkin in NYC.
01 of 08


suds on pink background

Sulfates are chemicals that are extremely common in our daily lives, as they can be found in many household cleaners and detergents. In haircare, they are usually found in shampoo where they are used to create a lathering effect. Dr. Markowitz explains that their bad reputation started long ago: "Sulfates' bad reputation started in the 1990’s when information began circulating that they can cause cancer, and the bad press continues today as more consumers lean toward natural beauty," she says.

Friese adds that sulfates are a petroleum product, and therefore are associated with climate change, pollution, and greenhouse gases. She also adds that many products containing sulfates are also tested on animals.

The Verdict: Dr. Markowtiz shares that "There is actually no scientific proof that sulfates cause cancer when found in haircare or skincare products," and Friese echoed this as well. The true risks of sulfates are irritation and dryness. "Sulfates can also strip your hair and scalp of its natural oils and if you already have sensitive skin, it can cause further irritation," Dr. Markowitz explains. She adds that if you have normal hair and skin, then using a shampoo with sulfates is okay and there are no downsides. "In fact, a shampoo with sulfates is the most efficient way to clean your hair because of the way it lathers," she says. "However, if you do have sensitive skin or eczema, using a sulfate-free shampoo would be beneficial."

02 of 08



Silicones can be found in every step of your haircare routine, from shampoos to finishing creams. They're popular for their ability to tame frizz and boost shine. Friese shares that they are non-toxic, can help prevent frizz, and can help with heat protection.

Dr. Markowitz explains that silicones get bad press in the dermatology and plastic surgery space because silicone injections and breast implants have been linked to autoimmune diseases. "Oftentimes when an ingredient is linked to a negative side effect in one area, it can have a ripple effect and people begin to question how safe it is in other products. When found in haircare or applied topically, silicone does not have the same implications as stated above," Dr. Markowitz explains.

The Verdict: When it comes to the truth about their bad reputation for hair, two of our experts shared reservations about using products with silicones for hair-specific reasons. Friese explains that over time, silicones can build up on your hair, resulting in a dry feel and dull appearance. They can also cause buildup and clog follicles, which can lead to hair loss. She also adds that "forms of silicone that aren’t water-soluble can be really hard to remove with just a regular wash and may require a clarifying shampoo." Dr. Markowitz shared a similar sentiment, saying "hair products with silicone leave behind a residue in your hair and scalp which weighs it down, blocks your hair follicles, and can cause hair loss." She recommends steering clear of products with silicones and working to remove the residue of silicones by using silicone-free shampoo. "I love the ColorWow Security Shampoo and Conditioner—it's a clean, residue-free formula. Also, ColorWow has an amazing product, Dream Filter, which removes minerals and pollutants from your hair."

03 of 08



Parabens are a group of chemicals that are used as preservatives in haircare and other beauty products. They are used in both rinse-off and leave-on products and are most commonly found in products that have a high water content, such as shampoos and conditioners. Their primary purpose is to prevent the growth of bacteria and mold. They have received negative attention because "in high concentrations, parabens can be an endocrine disruptor, are linked to cancer, and in a more common occurrence, cause skin irritation in people with conditions like eczema," Dr. Robinson explains.

The Verdict: While those are frightening accusations, Dr. Robinson says that "the amount found in most skincare products is not harmful to human health (per FDA), and the reality is parabens are sometimes necessary to act as a preservative to keep the product safe from growing pathogens like mold and bacteria." If you are looking to avoid parabens, there are many shampoos that are formulated without them.

04 of 08


pink Hair dye in a bowl

Hydroquinone is used in cosmetics as an antioxidant, fragrance ingredient, and oxidizing agent in hair dyes. Also known as quinol, this product is usually found in products for the hair and skin that are designed to lighten. Dr. Robinson shares that its bad reputation stems from the fact that "in high doses, it has been linked to cancer in studies done on rats." Additionally, it can cause skin irritation.

The Verdict: Hydroquinone is more commonly found in skincare products, but has been making its way into hair dyes and even conditioners. Dr. Robinson states that the FDA has confirmed that hydroquinone can be safely sold in 2% concentrations. She says that "when used at the correct concentration and dosage, and alongside accompanying ingredients, Hydroquinone is a safe and effective way to lighten hyperpigmentation," but more research is needed on its effects on hair.

05 of 08


liquid in dropper

Many hair products that are designed to smooth or straighten hair contain formaldehyde, formaldehyde dissolved in water (called methylene glycol), or other chemicals that can release formaldehyde during use. Dr. Robinson explains that it is added to water-based products to avoid the growth of microbes. Friese shares that the bad reputation of formaldehyde became widespread when hair care professionals who used products with it started becoming ill. She adds that "warnings from OSHA and the FDA have noted that products containing formaldehyde have been associated with reactions such as eye problems, nervous system problems, respiratory tract problems, nausea, chest pain, vomiting, and rash. It has also been labeled a probable carcinogen."

The Verdict: Both Dr. Robinson and Friese recommend avoiding formaldehyde if possible, especially in high doses. Dr. Robinson points out that formaldehyde is banned in cosmetic products in Japan and Sweden and regulated to specific low-dose concentrations in the EU and Canada. She cautions, "When you can, skip it!" 

06 of 08

DMDM Hydantoin


DMDM Hydantoin, also known as a formaldehyde donor, is an odorless, crystal-like substance that works as an antimicrobial agent, Dr. Markowitz explains. It is used as a preservative in personal care products to prevent the growth of bacteria. DMDM Hydantoin has received a lot of attention recently, as many consumers discovered it was a chemical that can release formaldehyde during use. Consumers reported experiencing hair loss after using products, like shampoo and conditioner, that contained DMDM Hydantoin.

The Verdict: Dr. Markowitz cautions that it has a bad reputation because it has been linked to hair loss and several haircare brands have had lawsuits filed against them where hair loss has been claimed. She says it has also been linked to dermatitis, so she advises that "If you have a history of skin diseases like eczema or other skin allergies, it may be best to steer clear from products with DMDM Hydantoin, however there is no scientific data of any long term side effects." Friese adds that "According to scientific research DMDM hydantoin is however a safe cosmetic ingredient when used at regulated levels. The amount of formaldehyde released from DMDM hydantoin is about the equivalent to the amount that naturally occurs in one medium sized apple or pear."

07 of 08


Phthalates in fragrance

Phthalates often are not found on an ingredient list, as they are considered part of the "fragrance" category. Phthalates are a group of chemicals used to make plastics soft and flexible. You can’t see, taste, or smell them, but they are in almost every product you use, including personal care products such as nail polish, cosmetics, fragrance and hair products. Dr. Markowitz explains that "In hair care, phthalates are used as solvents and perfume fixatives. They have a bad reputation because they are believed to interfere with reproductive function and hormonal systems." Dr. Robinson adds that this ingredient is actually banned in the EU and has been linked to endocrine disruption cancer and reproductive issues. 

The Verdict: All three of our experts agree that there is strong evidence to support the negative reputation of phthalates. Dr. Markowitz says "According to the FDA, there is no clear effect phthalates have on health, however in other countries the regulation on this ingredient is much stricter. There have been studies that prove Phthalates are an endocrine disruptor." Both Dr. Robinson and Dr. Markowitz recommend avoiding phthalates in hair care. Dr. Markowitz says that this should not be difficult to do, as many brands don't use this ingredient anymore. 

08 of 08


Petrolatum smear

Petrolatum is a byproduct of gasoline production that is most commonly referred to as petroleum jelly. In haircare products, you will most likely see this listed on an ingredient list as mineral oil. It is lightweight, colorless, odorless, and prevents moisture from escaping skin and hair. Most concerns around its use have to do with its ability to build up on the scalp and hair, weighing down hair and blocking new follicle growth. More serious concerns have to do with the manufacturing process, which includes polycyclic aromatic hydrocarbons (PAHs) that are considered to have potential links to breast cancer, Dr. Robinson explains.

The Verdict: Dr. Robinson shares that petrolatum is a mixture of natural mineral oils and waxes, and when used safely and as directed can improve wound healing and support of a compromised skin barrier. "PAHs are found in unrefined petroleum, while most commercial petroleum jelly products are made from refined petroleum jelly," which eases concerns about the most serious claims against petrolatum. However, the potential for buildup is a concern for dry or frizzy hair. To remove petrolatum from the hair and scalp, you will need to use a clarifying shampoo, which can be very stripping for curly or coarse hair.

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