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5 Toxins That Cause Hair Loss

Jill Johnson

Medically reviewed by Jill Johnson, FNP

Written by Our Editorial Team

Last updated 3/26/2023

You probably know that the right shampoo, conditioner and hair products can make the difference between dry, brittle hair and hair that grows thick, full and strong. But what you might not know is that some hair products are better for your hair than others.

While the U.S. Food and Drug Administration (FDA) regulates hair products to prevent dangerous ingredients and toxins from going into them, some formulas still contain chemicals that can potentially cause hair loss, hair damage and other issues.

Beyond shampoo and conditioner, you could be exposed to toxins that cause hair loss from common household items.

We’re certainly not trying to scare you. Instead, we’re here to provide useful information to help you get to the root of your hair loss.

Below, we’ll go over chemicals and toxins that cause hair loss in addition to steps you can take to avoid chemical-related hair loss. We’ll also discuss other potential causes of hair loss, from hormones and genetic factors to stress, illness and more.

5 Toxins That Cause Hair Loss

First, we should mention that most hair products sold in drugstores and online are safe to use and unlikely to cause hair loss.

There are a few ingredients in hair care products that can potentially harm your scalp and hair follicles, especially when used excessively or incorrectly. Hair loss may also be caused by long-term exposure to certain toxins from more common household items or occupational exposure.

Keep reading to learn about the toxins that cause hair loss and how you can minimize the damage from each potential source.

Formaldehyde

While this might sound like a chemical you don’t see very often, formaldehyde — a carcinogen that can cause irritation, allergic dermatitis and skin sensitivity — is a very common ingredient.

In fact, it’s used in many household products, such as glues, adhesives, permanent-press fabrics and certain insulation materials or as a preservative in cosmetic products.

Even when formaldehyde isn’t an ingredient in a product, substances that release formaldehyde might present — as is the case with shampoos or keratin-based hair-smoothing treatments.

While there’s no evidence supporting a link between formaldehyde and hair loss, some have noticed excessive shedding and hair thinning after using hair-straightening products.

The irritation caused by products that release formaldehyde might lead to scalp itching, potentially resulting in hair follicle damage.

To avoid exposing your hair to formaldehyde, ask your stylist about the ingredients in any hair smoothing or straightening treatments they use. You can also check the labels on your personal care products for formaldehyde and related ingredients, such as formalin and methylene glycol.

Hair Dye

While personal hair dye use is a fun way to switch up your look, using color or bleach weakens your hair, causing it to become more prone to breakage.

The ingredients in hair dyes — particularly ammonia and hydrogen peroxide — weaken the hair shaft by damaging the protein within, leading to shedding and/or breakage of existing hairs in the telogen stage.

To avoid breakage and loss from personal hair dye use, try to add time between touch-ups — every eight to 10 weeks or longer. You can also avoid hair dye use in the winter when the air is dryer.

Be sure to carefully follow the instructions provided if you’re dyeing your hair yourself. Otherwise, get your hair bleached and colored by an experienced professional.

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Medications

Some prescription drugs, including antimetabolites, mitotic inhibitors and alkylating agents used in chemotherapy, can cause a type of drug-induced hair loss called anagen effluvium.

This type of hair loss starts when hairs in the anagen phase of the hair growth cycle suffer from chemical toxicity or inflammation, preventing them from growing properly, usually within 14 days of medical treatment.

Unlike male pattern baldness, loss of hair from anagen effluvium is usually only temporary. It’s common for affected hair to grow back once it’s no longer exposed to medications that produce this type of hair shedding.

Heavy Metals

No, we’re not talking about rock music. Long-term exposure to heavy metals has been connected to alopecia — a form of hair loss.

A review of 47 articles and studies on alopecia found that heavy metals such as mercury and thallium were the top toxins that caused anagen effluvium. 

Other heavy metals linked to anagen effluvium include boron, thallium, cadmium, copper and bismuth. Heavy metal poisoning can occur from occupational exposure if your work involves manufacturing certain electronics, semiconductor materials and alloys.

You should look out for these metals if you work in an industrial environment. However, they aren’t used in hair care products, and as such, the risk of toxicity from heavy metal poisoning isn’t a major concern for most people.

Arsenic Poisoning

Another toxin that causes hair loss is chronic arsenicosis — or prolonged exposure to toxic levels of arsenic, a naturally-occurring metalloid found in soil, water and seafood.

The World Health Organization (WHO) estimates 140 million people worldwide are exposed to water containing potentially unsafe levels of arsenic.

According to the CDC (Centers for Disease Control and Prevention), workers in certain industries may also be susceptible to chronic arsenicosis, including glass manufacturing, agriculture and construction.

However, the risk of arsenic poisoning from environmental causes is unlikely to affect many people, partly due to the Environmental Protection Agency (EPA) setting a limit of 0.01 parts per million (ppm) for arsenic in drinking water.

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Other Causes of Hair Loss

Toxins aren’t the only cause of hair loss. Male pattern baldness (also known as androgenetic alopecia) is typically caused by a combination of genetic factors and your body’s production of male sex hormones, or androgens.

Specifically, hair loss from male pattern baldness is caused by a genetic sensitivity to the hormone dihydrotestosterone, or DHT, a byproduct of testosterone.

DHT plays a crucial role in puberty and is responsible for facial, pubic and body hair growth. It can also cause your hair follicles to gradually become weaker and, in some cases, stop producing new hairs as you get older.

Our complete guide on DHT and its effects on male hair loss goes into more detail on this process.

While male pattern baldness is the most common type of hereditary hair loss, there are other causes of hair loss.

Alopecia Areata

Alopecia areata is an immune system disease that causes hair loss. It’s thought to be a result of changes to certain genes in the hair and skin. Hair typically falls out in round patches, leaving small bald spots the size of coins.

Telogen Effluvium

Another type of hair loss, telogen effluvium, occurs after a stressful or traumatic event. These stressful events might include illnesses, metabolic stress, trauma, infection, surgery, hormonal changes, nutritional deficiencies or the use of certain medications.

Traction Alopecia

If your hair is long enough to tie back, traction alopecia can occur when you frequently choose hairstyles that pull on the roots of the hair. Hairstyles that put repetitive tension on the hair are the most common reason for this type of hair loss.

Tinea Capitis

Tinea capitis, or scalp ringworm, is a fungal infection that causes the loss of scalp hair. When the fungi that cause the infection penetrate the root sheath of the hair follicle, they may cause temporary hair loss. In some cases, tinea capitis can result in irreversible damage due to scarring.

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How to Prevent Hair Loss From Toxins

While the majority of chemicals in over-the-counter hair products will increase hair shedding, there are other toxins that cause hair loss. Here’s how you can try to prevent it.

  • If you indulge in personal hair dye use often, make sure you extend the time between coloring to prevent your hair from getting weak and breaking. You can also use conditioner after every time you color to moisturize your hair, which can improve its appearance and texture.

  • Avoid the use of keratin straightening products or other hair care products that use formaldehyde, which may increase irritation and hair thinning.

  • Check the labels of hair care products before you buy them. Although uncommon, some ingredients in consumer hair products may cause allergic reactions, irritation and even hair loss.

The best way to avoid damaging your hair is to use hair products that have scientific proof to support their effectiveness, such as our range of evidence-based hair products for men. You can also learn more effective hair care tips in our roundup of 18 men’s hair care tips.

If you’re starting to lose hair and think exposure to toxins is the culprit, you can learn more about your options to avoid further hair loss and stimulate new growth in our guide to male pattern baldness.

We also offer common prescription hair loss medications online, such as finasteride, minoxidil foam and minoxidil liquid, following a consultation with a licensed healthcare provider who’ll determine if a prescription is appropriate.

This guide on how a hair loss diagnosis works can also give more insight into what to expect.

16 Sources

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references.

  1. Formaldehyde in Hair Smoothing Products: What You Should Know. (2021, March 2). FDA. Retrieved from https://www.fda.gov/consumers/consumer-updates/formaldehyde-hair-smoothing-products-what-you-should-know
  2. Formaldehyde and Cancer Risk. (2022, October 24). American Cancer Society. Retrieved from https://www.cancer.org/healthy/cancer-causes/chemicals/formaldehyde.html
  3. Consumer Health Alert: Hair Straightening Products and Formaldehyde. (n.d.). New York State Department of Health. Retrieved from https://www.health.ny.gov/environmental/chemicals/formaldehyde/consumer.htm
  4. 10 hair care habits that can damage your hair. (n.d.). American Academy of Dermatology. Retrieved from https://www.aad.org/public/everyday-care/hair-scalp-care/hair/habits-that-damage-hair
  5. Bader, K. (2017, June 12). Does hair dyeing facilitate hair loss? Dermatology Times. Retrieved from https://www.dermatologytimes.com/view/does-hair-dyeing-facilitate-hair-loss
  6. Saleh, D., Nassereddin, A. & Cook, C. (2021, August 12). Anagen Effluvium. StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK482293/
  7. Yu, V., Juhász, M., Chiang, A., & Mesinkovska, N. A. (2018). Alopecia and Associated Toxic Agents: A Systematic Review. Skin Appendage Disorders, 4(4), 245-260. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6219226/
  8. Arsenic. (2022, December 7). World Health Organization (WHO). Retrieved from https://www.who.int/news-room/fact-sheets/detail/arsenic
  9. Arsenic | NIOSH | CDC. (n.d.). Centers for Disease Control and Prevention. Retrieved from https://www.cdc.gov/niosh/topics/arsenic/default.html
  10. Arsenic. (2007, August). Environmental Protection Agency. Retrieved from https://www.epa.gov/sites/default/files/2014-03/documents/arsenic_toxfaqs_3v.pdf
  11. Ho, C.H., Sood, T., Zito, P.M. (2022, October 16). Androgenetic Alopecia - StatPearls - NCBI Bookshelf. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK430924/
  12. Kinter, K.J., Anekar, A.A. (2022, March 9). Biochemistry, Dihydrotestosterone - StatPearls - NCBI Bookshelf. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK557634/
  13. Alopecia areata. (2018, June 1). MedlinePlus. Retrieved from https://medlineplus.gov/genetics/condition/alopecia-areata/
  14. Hughes, E.C., Saleh, D. Telogen Effluvium - StatPearls - NCBI Bookshelf. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK430848/
  15. Pulickal, J. K., & Kaliyadan, F. (2022, August 8). Traction Alopecia - StatPearls - NCBI Bookshelf. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK470434/
  16. Al Aboud, A. M., & Crane, J. S. (2022, August 8). Tinea Capitis - StatPearls - NCBI Bookshelf. NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK536909/

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.