What Chemicals Cause Hair Loss?

The right shampoo, conditioner and styling products can be the difference between a gorgeous head of hair and hair that’s dull, brittle and lifeless. 

While many ingredients used in hair care and styling products are healthy and effective, not all are good for your hair. 

Over the years, regulatory bodies like the FDA have done a good job of preventing harmful and dangerous ingredients from getting into consumer hair care products. However, a few products still contain chemicals that can potentially cause hair loss, hair damage and other issues.

Below, we’ve listed chemicals and other ingredients that are linked to hair loss, as well as some steps that you can take to avoid chemical-related hair loss from styling products.

We’ve also discussed some of the other potential causes of hair loss in women, from hormones and genetic factors to stress, illness, hair styling habits and more. 

In general, most hair products available in drug stores and online are unlikely to cause serious damage to your hair, especially damage that can cause hair loss.

However, there are a few ingredients in hair care products that can potentially harm your scalp and hair follicles, especially when they’re used excessively or incorrectly. We’ve covered these below and explained how you can minimize the effects of each potential source of damage.

Formaldehyde in Keratin Products

Many hair straightening products contain formaldehyde — a carcinogen that can cause irritation, allergic dermatitis, skin sensitivity and — when released in large quantities — headaches, cough, nausea, chest pain, rashes and vomiting.

While there’s no scientific research that shows a direct link between formaldehyde and hair loss, some people report noticing shedding and thinning after using these treatments. 

It’s possible that the irritation caused by products that release formaldehyde could result in scalp itching, which may damage your hair follicles.

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

Prescription 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. It usually starts within 14 days of treatment with prescription medication.

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

Thallium, Mercury and Other Metals

In addition to chemotherapy medications, some heavy metals are toxic to your hair follicles and may cause anagen effluvium hair loss.

Heavy metals that are linked with anagen effluvium include boron, thallium, mercury, cadmium, copper and bismuth. Many of these metals are used in jewelry, consumer products and some industrial supplies and equipment. 

While you might need to look out for these metals if you work in an industrial environment, they aren’t used in hair care products and as such, aren’t a major risk for most people.

Bleaches and Hair Dyes

If you have dark hair, you might have used bleach and dye before to lighten its tone and change its color. 

While most bleaches and hair dyes aren’t dangerous when used as recommended, some dyes and other coloring products may weaken your hair if overused, which could cause or contribute to hair thinning and noticeable hair loss.

Many dyes and hair coloring products can also cause other problems, including scalp irritation, redness, flaky skin and even blisters. If you have sensitive skin, even a small amount of direct exposure to some dyes may be enough to leave your scalp feeling itchy and uncomfortable.

To reduce your risk of hair loss or scalp irritation, follow the instructions provided with any dyes and other coloring products carefully, or get your hair bleached and colored by an experienced professional.

Strong Hold Hair Styling Products

Although technically not chemicals, some hair styling products may damage your hair follicles and cause a form of hair loss called traction alopecia.

This type of hair loss occurs when your hair follicles are pulled on, such as by dreadlocks, hair extensions or styles that may also rely on strong hold products. Even an overly tight ponytail can cause this form of hair loss, earning it the nickname ponytail hair loss.

If you style your hair using gel, wax or mousse, try replacing strong hold products with products that give your hair a softer texture and put less pressure on your hair shaft.

Alternatively, try going without any styling products — and either wearing your hair down or in a loose ponytail — every other day.

In addition to chemicals, a variety of other factors can play a role in hair loss, including genetics and hormones, chronic stress, traumatic experiences and infections that damage your skin and hair follicles.

Female Pattern Hair Loss

One of the most common causes of hair loss is female pattern baldness — a form of permanent hair loss that’s caused by the effects of the androgen hormone dihydrotestosterone (DHT).

Also referred to as androgenetic alopecia and hereditary hair loss, this type of hair loss occurs when DHT binds to receptors in your scalp and affects their ability to produce new hairs. Over time, this can result in diffuse, slow hair loss around your natural part line.

While chemicals in bleaches and hair styling products can potentially weaken your hair, they’re not involved in this type of hair loss. 

Pattern hair loss can be treated with minoxidil, a topical medication that’s believed to stimulate hair growth and can also increase blood flow to the scalp.

Stress, Trauma and Illness

Chronic stress, trauma, illnesses that cause fever, nutritional deficiencies and even fluctuations in your hormone levels can all cause a form of temporary hair loss called telogen effluvium.

Telogen effluvium occurs when your hairs rapidly change from the anagen, or growth, phase of the hair growth cycle into the telogen, or resting, phase. It usually causes diffuse thinning and can occur several months after the causative event.

Unlike female pattern hair loss, telogen effluvium isn’t permanent. Most of the time, the affected hairs grow back once the causative issue, such as stress or a nutritional deficiency, is treated.

Infections and Skin Inflammation

Some scalp infections, such as tinea capitis (scalp ringworm), can affect your hair follicles and cause temporary hair loss.

When infections become severe, they can cause severe inflammation and the development of an abscess called kerion. This can result in scarring that affects your hair follicles and causes permanent loss of hair.

Most scalp infections can be treated using topical or systemic medications. For example, tinea capitis is typically treated with antifungal drugs and shampoos.

Knowing which chemicals cause hair loss in addition to what ingredients are bad for hair can help you have healthier hair for days. If you’re concerned about chemical hair damage, making a few simple changes to your hair care routine can often have a big positive impact. Use the following tips to protect your hair and avoid chemical-related hair loss:

• Ask your stylist about products used to dye or reshape your hair. If you have your hair dyed, straightened or permed in a hair salon, ask your stylist about the ingredients used in their bleaches, dyes and styling products. 

• Check the labels of hair care products before you buy. Although uncommon, some ingredients in consumer hair products may cause allergic reactions, irritation and even hair loss.
  When you’re comparing shampoos, conditioners and other hair products, always check each product’s ingredient list before making a purchase. 

• Avoid using “strong hold” or “long-lasting hold” products. Instead, choose styling products that don’t pull on your hair roots. Avoid combing your hair after using products that add hold and thickness, as this may cause hair loss.

• Use conditioner after you shampoo. Conditioner helps moisturize your hair, which can improve its appearance and texture. Make sure to apply conditioner every time you shampoo your hair.

• Be careful when applying heat to your hair. If your hair is already damaged, applying heat can make it worse. Use your blow dryer infrequently and only ever use flat irons or other heat styling tools on a low to medium heat setting.

• Wait eight to 10 weeks between treatments. It’s okay to color, straighten or perm your hair, but it’s important to space out these treatments to avoid damaging the proteins that make up your hair and affect your hair health.
  Try to wait for eight to 10 weeks between touch-ups and chemical treatments. When you get your hair done, choose one service at a time — for example, a color treatment, perm or straightening.

Although some ingredients in hair care products can cause itching, irritation and other problems, it’s uncommon for chemicals in over-the-counter hair products to cause hair loss.

However, it’s important to be aware of potential sources of chemical hair damage, such as some medications, heavy metals and substances such as formaldehyde.

The best way to avoid damaging your hair is to stick with proven, evidence-based hair products, such as our range of evidence-based hair care products for women. 

If you’re starting to lose hair and think chemical exposure could be to blame, you can learn more about your options for limiting further hair loss and stimulating new growth in our guide to female hair loss.