Do some ingredients in shampoo do more harm than good? Is shampoo even necessary?
Here, dive into why some hair-washing ingredients can be damaging to hair and health, which shampoo ingredients to avoid, and what experts say about over-washing.
Shampoo is a cleansing product that removes oil, sweat, product buildup, and dirt from your hair and scalp. It’s distinct from regular soap in that it lathers and cleanses without leaving a residue on your hair when mixed with hard water.
There are different shampoo formulas and types (such as bars, powders, liquids, and sprays), and many are created with the secondary goal of making hair manageable and attractive.
Shampoos also clean the scalp and hair of environmental pollutants, germs, and odors, says Shari Lipner MD, PhD, an associate professor of clinical dermatology and dermatologist at NewYork-Presbyterian and Weill Cornell Medicine in New York City. “The challenge is to remove just enough oils so that the hair looks, feels, and smells clean, but leaves behind enough conditioning agents to leave the hair soft, shiny and manageable.”
There are several common ingredients that are found in most shampoos, says Rebecca Kazin, MD, a dermatologist and the director of clinical research at Icon Dermatology and Aesthetics in North Bethesda, Maryland. She says these include:
Surfactants These are the primary cleaning agents in shampoos that help to break down oils and dirt and allow these substances to be washed away.
Conditioning Agents These ingredients help to soften the hair, making it easier to manage.
Thickeners These ingredients give shampoo its desirable consistency.
Preservatives These prevent microbial growth and extend the shelf life of shampoo.
PH Adjusters These help maintain the pH balance in shampoo, which is important for hair and scalp health.
Fragrance and Colorants These ingredients aren’t essential, but they enhance user experience by providing a pleasant look and scent to shampoo.
Botanical Extracts and Oils These can provide additional benefits such as moisturizing properties or soothing effects.
Some shampoos also contain ingredients to treat scalp conditions such as seborrheic dermatitis.
Some ingredients frequently used in shampoo can be harmful to your hair or even your health.
Shampoo Ingredients That Can Hurt Hair
Experts say skip shampoos with these ingredients, as they may be damaging to hair.
1. Alcohol(Some of Them)
Alcohol is commonly found in shampoos, conditioners, and styling products because it helps your skin and hair absorb active ingredients. But short-chain alcohols (including isopropyl alcohol) can irritate the skin and dry out the hair, according to Consumer Notice, a nonprofit consumer advocacy organization that educates the public about harmful products. Ethanol is another short-chain alcohol that can also leave the hair feeling dry and brittle, says Ross Kopelman, DO, a hair restoration surgeon with Kopelman Hair Restoration in New York City.
That said, fatty alcohols like cetyl alcohol, stearyl alcohol, and cetearyl alcohol have the opposite effect. “They help condition the hair and retain moisture,” says Dr. Kopelman, who notes that fatty alcohols can be especially helpful for people with dry or damaged hair.
2. Coal Tar
Coal tar is a petroleum by-product that’s used in permanent hair dyes, with darker dyes containing higher amounts. It’s commonly added to shampoos to treat scalp psoriasis.
There’s some concern that coal tar may be a carcinogen, but the American Cancer Society notes that studies haven’t found a strong link so far. “Dermatologists prescribe coal tar shampoos for scalp psoriasis if needed and it is considered safe for long-term use,” Dr. Kazin says. Note, however, that using the products too often or on a sensitive scalp may cause hair loss or burning, itching, tingling, pain, or redness.
People who are pregnant or breastfeeding should avoid coal tar in psoriasis shampoos and hair dyes altogether, given the lack of research on its effects in this group, Kazin says.
3. Polyethylene Glycols
Polyethylene glycols (PEGs) are petroleum by-products used to thicken hair care products. Past research shows PEGs are generally safe when used in cosmetics.
But researchers are still examining a potential link between PEGs and severe scalp irritation and skin damage. Moreover, some PEGs may be contaminated with harmful substances like 1,4-dioxane, which is a known carcinogen, Kopelman says.
PEGs can be listed on product labels in different ways. They often appear as “PEG” followed by a number (such as PEG-40) or “PEG” followed by a number and then another ingredient name (such as PEG-20 cocamine).
4. Selenium Sulfide
Selenium sulfide, an anti-infective agent, is often used in medicated shampoos to treat dandruff-related itching and flaking. But this ingredient can irritate the scalp and cause permanent hair loss if used too frequently.
“I generally advise patients to limit their use of selenium sulfide to two to three times per week at most,” Kopelman says. If your scalp becomes more sensitive or you notice hair thinning, alternate the selenium sulfide shampoo with a gentler shampoo that contains zinc pyrithione or tea tree oil, suggests Kopelman.
5. Silicones
Silicones are added to hair-care products to make your hair soft and smooth. But these ingredients build up with repeated use, preventing moisture from getting into your hair cuticles. This can cause skin irritation, dry hair, and flat curls.
Check hair-care product labels for these common silicones:
Dimethicone
Phenyl trimethicone
Cyclomethicone
Cyclopentasiloxane
Cyclohexasiloxane
Shampoo Ingredients That May Be Damaging to Overall Health
Many shampoo ingredients that can be harmful to the hair and to overall health have become much less common as research by dermatologists has highlighted the risks and products have been reformulated, says Mary Lupo, MD, a dermatologist at the Lupo Center for Aesthetic & General Dermatology in New Orleans.
But several potentially harmful ingredients are still regularly found in shampoos, including the following.
1. Benzene
Benzene is a colorless liquid chemical that’s commonly used in hair dyes. It may be carcinogenic with long-term use, and may contribute to birth defects and damage the immune and nervous system in people who are pregnant.
In October 2022, the U.S. Food and Drug Administration (FDA) found elevated levels of benzene in dry shampoo products. In response, dry shampoo manufacturers pulled benzene-containing products from store shelves. Since you may have purchased these products before they were recalled, be sure to check the label of any dry shampoo you have at home.
To ensure your hair product doesn’t include benzene, check the label for these ingredients:
Benzene
Toluene
Methylbenzene
Phenylmethane
Toluol
2. Resorcinol
Resorcinol is a bleaching agent commonly found in hair dyes and treatments for dandruff and scalp psoriasis. It may interfere with the creation of thyroid hormones, impacting thyroid function and increasing the risk of hyperthyroidism (where the thyroid creates too many hormones). Resorcinol may also cause breathing problems and disrupt the nervous system.
“Ultimately, it’s about balancing effectiveness with safety, and for patients with chronic scalp conditions, I encourage discussing options with a dermatologist or hair specialist,” Kopelman says.
To avoid resorcinol, check hair dyes and products for the following ingredients:
Resorcinol
1,3-benzenediol
Resorcin
1,3-dihydroxybenzene
3. Diethanolamine
Diethanolamine (DEA), commonly used as a foaming agent or to adjust the pH balance in hair products, is a possible carcinogen. Research has found a link between DEA and cancer in laboratory animals, but not humans. “DEA is classified as a potential allergen but the FDA does not restrict it for health reasons,” Kazin says.
4. Triclosan
Triclosan is an antibacterial agent that was used in soaps — until data suggested that long-term exposure could disrupt hormones. This led the FDA to ban triclosan from antibacterial soaps in 2016. But triclosan is still used as an antibacterial agent in shampoos.
5. Formaldehyde and Formaldehyde-Releasing Preservatives
Formaldehyde is a colorless, strong-smelling gas found in cigarettes, building materials, and industrial cleaning products. It’s also added directly to or released from preservatives in shampoo and chemical hair-straightening treatments, and is linked to an increased risk of cancer.
Formaldehyde and formaldehyde-releasing preservatives can also cause allergic skin reactions.
Check shampoo, conditioner, and chemical hair straightener labels for formaldehyde (also referred to as methylene glycol and formalin) and preservatives that release formaldehyde. These include:
Quaternium-15
Imidazolidinyl urea
Diazolidinyl urea
Polyoxymethylene urea
Sodium hydroxymethylglycinate
Glyoxal
6. Parabens
There’s concern that parabens, which help extend the shelf life of shampoo, may disrupt your hormone balance, reproductive health, and nervous system and cause skin irritation. The FDA says no research currently shows that parabens affect human health.
In addition, research shows that parabens are less likely than other preservatives to cause allergic reactions, Kazin says.
Still, if you’d like to avoid hair products with parabens, check the label for ingredients ending in “paraben,” such as:
Butylparaben
Ethylparaben
Methylparaben
7. Synthetic Fragrances
Many manufacturers use fragrances to give shampoo and conditioner a pleasant scent. But these fragrances are often synthetic and may be created with chemicals that harm your skin, hair, and health. These chemicals may contribute to infertility, skin irritation, hair loss, asthma, and cancer.
“Fragrance blends often contain dozens of unlisted chemicals, which makes it difficult to determine exactly what you’re putting on your scalp,” says Kopelman. “While not everyone will have a reaction, I recommend patients opt for fragrance-free or naturally scented shampoos when possible, especially if they have scalp sensitivity, hair thinning, or hormonal concerns.”
To determine whether a shampoo has synthetic fragrance, Kopelman suggests checking the ingredient list for terms like “fragrance” or “parfum.”
8. Phthalates
Research suggests that phthalates, which enhance the fragrance of shampoo, may disrupt hormones. Pthalates are banned in Canada, but don’t need to be named on U.S. ingredient labels — they can simply be listed as “fragrance.”
Some companies label their products “phthalate-free.” Otherwise, check for these phthalates:
Butyl benzyl phthalate (BBP)
Diethyl phthalate (DEP)
Diisodecyl phthalate (DIDP)
Diisononyl phthalate (DINP)
Dihexyl phthalate (DHP)
Dioctyl phthalate (DNOP)
9. Sulfates
Sulfates, which create lather and bubbles in shampoo, can irritate the skin and eyes and trigger an allergic reaction. These ingredients can also dry out the skin and make hair frizzy.
Sulfates commonly used in shampoos include:
Ammonium lauryl sulfate
Sodium lauryl sulfate (SLS)
Sodium laureth sulfate (SLES)
SLES in particular may contain traces of 1,4-dioxane, a carcinogen that has contributed to cancer development in lab animals.
Even if your shampoo is free of the harmful ingredients above, you still don’t want to overdo it. Over-shampooing, or washing too frequently, can leave you with frizzy, dry, or dull hair. “When you over-shampoo, the hair and scalp can become drier and, hence, more irritated,” Lindsey Bordone, MD, a board-certified dermatologist and an assistant professor of dermatology at Columbia University Irving Medical Center in New York City.
Excessive split ends are another sign you’re washing too much, as over-washing can make your hair more susceptible to breakage. The best way to restore your natural oils is to simply take a break between washes.
Some people have adopted the #nopoo trend (where people rinse but skip the shampoo), choosing to clean the hair with baking soda and apple cider vinegar or water only, because they believe over-washing leads to an unnecessary reliance on shampoo and strips away the hair’s natural oils, per the No Poo Method website.
Forgoing shampoo sometimes leads people to load up on products such as dry shampoo to extend how long they can go without washing the hair, and that can create even more buildup on the scalp, Dr. Bordone says. “This can also lead to irritation from the product residue,” she says.
Experts say how often you wash your hair should depend on a variety of factors, including your hair type and your lifestyle.
Here are a few tips to best care for your hair.
Read product labels. Cross-check the ingredients listed on your shampoo bottle with those to avoid. Some ingredients, such as sulfates and parabens, may be bad for your hair and your overall health.
Look for healthier ingredients. Beneficial ingredients include biotin to strengthen hair and promote growth, keratin to repair and strengthen damaged hair, panthenol (vitamin B5) to moisturize and add shine, and natural oils like argan oil, coconut oil, or jojoba oil as another way to add moisture and shine, Kazin says.
Don’t get too hung up on the price of your shampoo. You don’t necessarily need to spend a ton of time washing your hair or a lot of money on shampoo to get the results you want. “More expensive is not necessarily better,” Dr. Lipner says. “More expensive shampoos may have higher concentrations of conditioners, but since most people use a conditioner anyway, less-expensive shampoos cleanse the hair well and are fine to use.”
Find the right washing frequency. There’s no tried-and-true recommendation for how often to shampoo your hair. The right frequency depends on your ethnicity, hair density, thickness, and growth rate, Bordone says. For example, oily hair may need washing daily or every other day, while dry hair may only need to be washed twice weekly, Kazin says. Curly hair can also be washed less frequently, sometime as little as once a week, Kazin adds.
Use your fingertips to wash. Use your fingertips to get a good lather from shampoo and scrub your scalp, Dr. Lupo says. If you use your fingernails, this can disrupt the protective layer on your scalp that maintains proper hydration, Lupo says.
Shampoo is designed to remove oil, sweat, product buildup, and dirt from your hair and scalp without leaving a residue on your hair when mixed with hard water.
Some shampoo ingredients can be harmful to your hair and overall health.
Over-washing the hair can also cause issues, including hair dryness and breakage and scalp irritation.
