Why Does Chemotherapy Cause Hair Loss?

Hair loss is a common side effect of chemotherapy treatment. This is because chemotherapy targets rapidly-dividing cells throughout the body, aiming at the cancer but also affecting the healthy cells that produce hair on the scalp and all over the body.

This hair loss generally starts to happen a few weeks after chemotherapy starts and will be experienced by most people (but not all). The hair usually grows back at least partially, and hair regrowth begins not long after chemotherapy treatment has ended. Knowing what to expect can help you prepare for chemotherapy.

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Chemo's Effect on Cells

Cancer cells tend to divide very quickly—at a much higher rate than most of the cells in the body. They ignore the signals and mechanisms that tell normal cells to stop dividing.

Some normal cells in our bodies also rapidly divide, like hair follicle cells, the mucous membrane cells lining of the digestive tract (mouth, throat, stomach, intestines), and the blood-producing cells in the bone marrow.

Chemotherapy drugs work by targeting rapidly dividing cells. They damage the genetic material inside cells (RNA and DNA) that guide cell division. Chemotherapy drugs cannot tell the difference between these normal, rapidly dividing cells and cancer cells, so the drug affects these cells as well.

The hair follicles have a good blood supply, which unfortunately allows chemotherapy drugs to reach them efficiently. About 65% of people who receive chemotherapy will experience hair loss. The amount of hair loss can depend on which chemotherapy agent is used, as well as the timing, dose, and route of administration. It can also vary from person to person, and it's hard to predict who will be affected most.

About 90% of your scalp hair is in the active growth phase (anagen) at any one time. This hair will be affected by chemotherapy agents.

There are five classes of chemotherapy drugs, each of which affects a different part of the cell growth cycle or acts in a different way. Which agent is chosen depends on the type of cancer.

Alkylating Agents

Alkylating agents damage the cell DNA at all phases of the cell growth cycle. They are used for breast, lung, and ovarian cancer as well as blood cancers.

Agents more likely to cause hair loss include Cytoxan (cyclophosphamide) and Busulfex (busulphan). The platinum metal salts, such as Paraplatin (carboplatin) and Platinol (cisplatin) are less likely to cause hair loss.

Antimetabolites

Antimetabolites impersonate the building blocks for RNA and DNA, keeping the genetic material from making copies of itself, so the cell can't divide. They are used for breast, ovarian, and colon cancer, as well as leukemia.

Adrucil (fluorouracil) and Gemzar (gemcitabine) are more likely to cause hair loss, while methotrexate is less likely to do so.

Anti-Tumor Antibiotics

Anti-tumor antibiotics act on the ability of cells to make copies of DNA, inhibiting cell growth and division. They are used to treat many types of cancer.

Among these, Cosmegen (dactinomycin), Adriamycin (doxorubicin), and Idamycin (idarubicin) are more likely to cause hair loss, while Bleo 15K (bleomycin), and Mutamicin (mitomycin C) are less likely to do so.

Topoisomerase Inhibitors

Plant alkaloids (topoisomerase inhibitors) target specific enzymes that enable DNA strands to separate and make copies of themselves. They are used for lung, ovarian, colorectal, and pancreatic cancer, as well as some leukemias.

Among this group, more hair loss is seen with VePesid (etoposide) and Camptosar (irinotecan) and less with Novantrone (mitoxantrone) and Hycamtin (topotecan).

Mitotic Inhibitors

Other plant alkaloids are mitotic inhibitors. They inhibit enzymes that are needed for cell reproduction. These include the taxanes (made from the bark of the Pacific yew tree) and vinca alkaloids (derived from the periwinkle plant). They are used for breast, lung, and blood cancers.

These chemotherapy agents are more likely to cause hair loss. They include Taxol (paclitaxel), Taxotere (docetaxel), Ellence (epirubicin), Ixempra (Ixabepilone), Ellence (epirubicin), Vincasar (vincristine), and Alocrest (vinorelbine).

Is Radiation Contributing to My Hair Loss, Too?

Some people receive both radiation and chemotherapy treatments, and both can contribute to hair loss. Radiation affects hair only on the body area that is treated. This may mean the hair on that area is lost, but not the hair on your scalp (although that may be affected by chemotherapy). At lower doses, radiation hair loss is temporary, but at higher doses it can be permanent.

Variation in Effects

Some of the newer cancer drugs are more precise in targeting cancer cells and may not result in hair loss. As well, there are varying degrees of hair loss, regardless of chemotherapy drug type and regimen.

Chemotherapy Hair Loss Timeline

Hair loss usually doesn’t happen immediately after chemotherapy. Instead, it may start after a few treatments.

A study of people with breast cancer treated with chemotherapy found that 99.9% experienced hair loss, beginning at day 18 of treatment, on average. Only 4% still had hair loss after two years.

Timeline for Hair Loss

  • 1 to 3 weeks after the first treatment: Hair loss begins.
  • 1 to 2 months: Hair loss becomes severe.
  • 3 to 6 months after treatment ends: Hair regrows.

What to Expect

Hair may fall out in clumps or seem like it is thinning as you lose a few strands at a time from all over your scalp. Depending on the type of chemotherapy used, you could lose the hair on your head only, or also on all parts of your body, including the eyelashes and eyebrows, arm, legs, underarms, and pubic area.

Other symptoms you may experience include:

  • Your scalp may feel itchy, tender, dry, or have increased sensitivity due to the effects of chemotherapy. A gentle cream or lotion may help.
  • Chemotherapy can make your skin more sensitive to the sun. Wear sunscreen with at least sun protection factor 30, including on your scalp, and wear a hat when outdoors.
  • You may note red or darkened skin or other pigmentation changes.
  • Your remaining hair may be dull or dry.

Can I Prevent Hair Loss From Chemo?

While hair loss may depend on the chemotherapy drug used and how the treatment is given, these choices are appropriately made to be the most effective against the type of cancer being treated.

One preventive measure is the use of scalp cooling. This can be done with ice packs, cooling caps, or scalp cooling systems used before, during, or after treatment. This causes the capillaries supplying the hair follicles to constrict, so they are exposed to less of the chemotherapy medication.

The effectiveness of scalp cooling is still being studied, but devices have been approved by the Food and Drug Administration. It seems to work best for taxane-based chemotherapy.

Using Rogaine (minoxidil) has not been shown to prevent hair loss, but it may reduce the severity or shorten the time it takes to regrow the hair .

Being gentle with your hair and scalp can help reduce hair loss and breakage, as well as prevent scalp irritation. Follow these tips:

  • Do not shampoo frequently.
  • Use warm water to clean your scalp, and pat dry rather than rubbing.
  • Use mild shampoos and conditioners that do not have perfumes. Avoid any hair products such as hair spray, gels, or oils.
  • Be gentle and keep combing or brushing to a minimum.
  • If you must use a hairdryer, use a low heat setting. Don't use a curling iron.
  • Avoid using brush rollers to curl or set hair, as well as any style where you pull the hair back with ponytail holders or hairbands.
  • Don’t dye your hair or get a perm.
  • Try sleeping on a satin pillowcase.

Hair Growth After Chemo

With most types of chemotherapy, the cells in the hair follicles will regenerate enough to resume hair growth. They normally go through a cycle of active growth, then rest. Chemotherapy sends more of them into the rest phase (telogen), which usually lasts for 100 days.

Some people will note hair beginning to come back even before the end of treatment, but it is more common to see it growing back after two to three months. At first, you may see light amounts of fuzz-like hair return, followed by thicker amounts of hair.

By about six months after treatment, you may have enough hair to be able to style it. A study of people undergoing breast cancer treatment found that about half stopped wearing a wig by the one-year mark and only 15.2% still wore a wig at the two-year mark.

Still, some people do not see hair regrowth. Some types of chemotherapy (such as busulfan and cyclophosphamide) have a higher risk of permanent hair loss.

The effects of chemotherapy on the hair follicles can result in the regrown hair being a different color or texture, and having different waves or curls than before. In the breast cancer treatment study, 53% said their hair became wavier or curlier, 58% reported thinner hair, 6% noted thicker hair, 38% said their hair was grayer or whiter, and 5% reported darker hair.

A Word From Verywell

Hair loss is a consequence of cancer treatment that many people dread. There is no right or wrong way to feel about this hair loss or how you face it. It can strike at the self-esteem and emotional well-being of many people, while others can view it as a symbol of their fight against the disease.

Talk to your treatment team about your risks, options, and their recommendations. You can choose to wear a wig or head covering, or embrace the new look. Many have been down this same path and can offer helpful suggestions and support.

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