What you may have heard
Shampoo with formaldehyde is a carcinogen.
What science tells us
Many hair care products, such as shampoos and leave-in conditioners, contain formaldehyde or other variations, such as formalin and methylene glycol. When these products are heated, the formaldehyde is released into the air as a gas. This can occur by blow-drying, straightening, or curling the hair.
Formaldehyde is a colorless, strong-smelling gas that presents a health hazard when inhaled.
According to the National Cancer Institute, when more formaldehyde is in the air than 0.1 part-per-million (ppm), some people may experience negative health effects, such as watery eyes; burning sensations in the eyes, nose, and throat; coughing; wheezing; nausea; and skin irritation (NCI).
Skin sensitization or allergic dermatitis can develop after repeated exposure to formaldehyde-related ingredients and when released into the air, it can cause irritation of the eyes, nose, and lungs (NCI).
The greater (and longer) the exposure to formaldehyde, the higher the health risks. For example, if a salon is not properly ventilated, both salon professionals and its clients are at risk of inhaling the released formaldehyde (FDA). OSHA issued a Hazard Alert to hair salon owners and workers about potential formaldehyde exposure and set a standard (29 CFR 1910.1048) limiting the allowable exposure in the air.
Several human studies of formaldehyde suggest that long term exposure can cause hematolymphopoietic cancer s including leukemias and lymphomas (Swenberg et al.)
Laboratory Evidence/ Supportive Evidence
Several laboratory studies have also used rat models, which concluded that long term formaldehyde exposure results in nasal cancer (NCI).
IARC Carcinogen Classification: Group 1 (carcinogenic to humans: Formaldehyde)
How to reduce your risk
If you are concerned about skin or eye irritation from products with formaldehyde, you may want to switch to products that do not contain these chemicals. Formaldehyde may not be listed on a product’s ingredients, but there are two formaldehyde-related ingredients that may produce similar effects: formalin and methylene glycol.
A number of websites, such as the Environmental Working Group’s Skin Deep Database or MADE SAFE, rate the safety of ingredients used in personal care products. These websites also post lists of brands that contain certain chemicals. The smartphone app Detox Me includes many tips to help you choose safer products.
A dermatologist and/or pharmacist may also be able to direct you to products that do not contain chemicals you wish to avoid.
You may report any adverse health reactions directly to the FDA using this link: FDA MedWatch Adverse Event Reporting System.
People who work in salons are at an increased risk of cancer due to repeated exposure to formaldehyde gas, which is produced when shampoos with formaldehyde are heated. Consider switching to formaldehyde-free shampoos.
Learn More From These Trusted Sources
Environmental Working Group (EWG): Skin Deep Database
Food & Drug Administration (FDA): Formaldehyde and hair products
National Cancer Institute (NCI): Formaldehyde and cancer
OSHA: Formaldehyde in hair salons
Published: July 9, 2021
Verified/updated: August 22, 2022