Hair loss occurs because chemotherapy targets all rapidly dividing cells—healthy cells as well as cancer cells. Hair follicles, the structures in the skin filled with tiny blood vessels that make hair, are some of the fastest-growing cells in the body. If you're not in cancer treatment, your hair follicles divide every 23 to 72 hours. But as the chemo does its work against cancer cells, it also destroys hair cells. Within a few weeks of starting chemo, you may lose some or all of your hair.
If you are having chemotherapy, your hair loss may be gradual or dramatic: clumps in your hairbrush, handfuls in the tub drain or on your pillow. Whichever way it happens, it's startling and depressing, and you'll need a lot of support during this time.
Some chemotherapy drugs affect only the hair on your head. Others cause the loss of eyebrows and eyelashes, pubic hair, and hair on your legs, arms, or underarms.
The extent of hair loss depends on which drugs or other treatments are used, and for how long. The various classes of chemotherapy drugs all produce different reactions.
The timing of your treatments will also affect hair loss. Some types of chemotherapy are given weekly and in small doses, and this minimizes hair loss. Other treatments are scheduled every three to four weeks in higher doses, and may be more likely to cause more hair loss.

Chemotherapy drugs

• Adriamycin (the “A” in CAF chemo treatment) causes complete hair loss on the head, usually during the first few weeks of treatment. Some women also lose eyelashes and eyebrows.
• Methotrexate (the “M” in CMF chemo treatment) thins hair in some people but not others. And it's rare to have complete hair loss from methotrexate.
• Cytoxan and 5-fluorouracil cause minimal hair loss in most women, but some may lose a great deal.
• Taxol usually causes complete hair loss, including head, brows, lashes, pubic area, legs, and arms.

Other types of breast cancer treatments may also cause hair loss. For example,

Radiation treatment

Radiation only causes hair loss on the particular part of the body treated. If radiation is used to treat the breast, there is no hair loss on your head. But there might be loss of hair around the nipple, for women who have hair in that location. Radiation to the brain, used to treat metastatic cancer in the brain, usually causes complete hair loss on the head.

Hormonal treatments

Tamoxifen may cause some thinning of your hair, but not baldness.
No matter how forewarned you are and how ready you think you are, it's always a terrible shock when your hair falls out.

Expert Quote

"There are studies that show that for many women, losing their hair is worse than losing a breast. That's because you can conceal the loss of a breast, but hair loss is so obvious and apparent."
-- Marisa Weiss, M.D., chief medical officer, Breastcancer.org

For women with breast cancer, dealing with the diagnosis can be challenging.
And the treatment itself can be equally challenging.
If the treatment includes chemotherapy, women face another possible issue: Hair loss.
Scientists are working on the problem.
Some solutions, like Rogaine, have been around for a while. Others, like skullcaps, have come into vogue the past year.
Read more: Stages of hair loss »

Why treatment causes hair loss

Chemotherapy drugs, including doxorubicin, paclitaxel, and docetaxel, “almost always cause hair loss,” said Dr. Nicole Williams, a breast medical oncologist with The Ohio State University Comprehensive Cancer Center – Arthur G James Hospital and Richard J Solove Research Institute.

“Hair loss occurs because chemotherapy agents are directed at rapidly dividing cancer cells, but other rapidly dividing healthy cells, such as hair follicles, are also affected,” Williams told Healthline. “Hair follicles are some of the fastest growing in the body.”
Within two to four weeks of starting chemotherapy, women may lose some or all of their hair.
Sometimes the loss is gradual. Other times, it’s sudden.
Some chemotherapy medications affect only the hair on the head, but others can cause loss of body hair including eyebrows and eyelashes.
Hair loss only occurs in areas where radiation is directed.
About a month or so after the treatment ends, the hair typically grows back, although it may be a different color or texture. A few months after, it often returns to its normal texture.
Chemotherapy isn’t the only cancer treatment that causes hair loss. Hormonal therapy such as tamoxifen or aromatase inhibitors may cause hair thinning.
Read more: Treating breast cancer without chemotherapy »

Preventing hair loss

How can women prevent hair loss?
Cold caps are growing in popularity, and one was cleared last December by the U.S. Food and Drug Administration (FDA).
The DigniCap scalp-cooling system reduces the likelihood of chemotherapy-induced hair loss.
The Mount Sinai Health System (MSHS) is using the cap at three of its cancer center locations.
In this treatment, the patient puts on the silicone cap, which is covered with a neoprene cap to insulate and secure it.

The cap is then connected to a unit that controls a coolant that circulates through the headwear. This works by lowering the scalp’s temperature and restricts how much chemotherapy gets to the scalp.
The cap is worn before, during, and after treatments.
In clinic trials, seven out of 10 patients with early stage breast cancer retained about 50 percent of their hair when using the system.
It was tested at Mount Sinai, where Dr. Paula Klein, an associate professor of oncology and hematology at the Icahn School of Medicine at Mount Sinai, studied it.
“If you cool the scalp, the chemotherapy doesn’t get there. It’s purely mechanical,” Klein told Healthline.
It’s not the only scalp-cooling technique that’s used. Others, however, were more complicated to use and cold on the head, Klein said.
They also had to be rotated every 20 or 30 minutes, which became cumbersome.
The DigniCap is not as complicated to use. It is only for early stage breast cancer patients receiving chemotherapy, Klein noted.
DigniCap costs vary depending on how much chemotherapy is needed, but they run about $1,000 to $3,000 for an entire chemotherapy cycle.
Insurance companies are starting to offer some coverage for the treatment and some medical centers offer financial assistance.
HairToStay.org is a nonprofit organization that offers financial assistance to patients.
Read more: Breast cancer genome could lead to personalized treatments »

Other options

Dr. Rebecca Moroose, director of the Office of Clinical Trials, and medical director for Cancer Genetics at UF Health Cancer Center at Orlando Health, said the cold caps are not the only therapy to help reduce hair loss during chemotherapy.

Some women apply minoxidil, or Rogaine, to their scalps before or after treatment. While it does little to prevent hair loss, some people say it can speed up re-growth.
Williams said some patients cut their hair prior to chemotherapy because the shorter locks may look fuller.
During treatment, women should wash their hair less often and use a gentle shampoo to cleanse it.
Many cancer centers provide resources for wigs. They also recommend scarves and caps for head coverings after hair loss.
While there are not many options for chemo-related hair loss, scalp cooling does offer hope to women who dread losing their hair.
“There is no treatment that will guarantee hair loss prevention during chemotherapy,” Williams said. “Several treatments have been investigated as possible ways to prevent hair loss, but none has been absolutely effective.”