Why does hair fall out in chemotherapy?

Side Effects of Chemotherapy

One of the common side effects of cancer treatments is hair loss. Although this side effect is reversible in most cases, it sometimes causes a significant emotional impact, which can lead to rejection and delay of chemotherapy treatment.

Why does chemotherapy cause hair loss?

Chemotherapy attacks rapidly dividing cells, such as cancer cells, but this property is not exclusive to cancer cells. Other cells in our body, such as hair cells are also rapidly dividing cells.

Hair loss due to chemotherapy is produced mainly by two mechanisms:

1. By severely preventing the division of keratinocytes (hair cells) in the hair follicle matrix; this causes the hair to separate at the bulb and fall off. This process is called anagen effluvium.

Depending on the toxicity of the drug, dose, and administration schedule, anagen effluvium can be severe, with rapid hair loss but rapid growth, or it can be partial, dystrophic anagen effluvium, with slow hair loss and delayed growth in hair.

2. Producing a thinning of the hair shaft, which can cause the hair to break at the follicular orifice.

What does hair loss during chemotherapy depend on?

The treatments used against cancer are very diverse, as are their side effects. Although alopecia is a common side effect of many of these treatments, its severity and how quickly it occurs depends on several factors:

1. Chemotherapy agent

Some chemotherapy agents cause more severe alopecia than others, such as doxorubicin and docetaxel compared to others that produce it more mildly, such as oral vinorelbine, cyclophosphamide or therapies directed against molecular targets (palbociclib, erlotinib, sunitinib... ).

2. The administration schedule

Schemes with high doses, intravenous, and intermittent administration, and those that combine several drugs, cause more severe and rapid-onset alopecia. It usually starts two weeks after the first administration and by the end of the second cycle it is practically complete.

However, low-dose drugs, administered orally, and weekly intravenous cytotoxic agents, usually produce less severe alopecia with a slower and more progressive onset.

Is hair loss reversible?

Hair usually grows back when treatment is stopped. This is because chemotherapy acts on proliferating cells and does not affect the stem cells of the bulb, which are responsible for follicular growth.

The hair follicle recovers its growth cycle several weeks after the suspension of the treatment and the recovery of the hair becomes visible in 3-6 months. However, permanent partial alopecia has been described after the administration of some cytostatics, such as docetaxel, although its frequency is low.

Can hair loss be prevented?

There are cold caps to prevent and reduce the severity of alopecia caused by chemotherapy, with greater evidence in patients with breast cancer treated with chemotherapy regimens and anthracyclines. However, its effectiveness is mixed: less than 50% of patients retained at least 50% of their hair.

If you have doubts or concerns about chemotherapy, please reach out, we are here to support you.

Article written by:

Dr. Natalia Eres. Medical Oncologist in the area of ​​Ecomedicine and Holistic Oncology. Director of the Imohe Institute.