Is Your Shampoo Harming Your 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.

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. Experts say skip shampoos with these ingredients, as they may be damaging to hair.