Many people undergoing chemotherapy will lose their eyebrows and eyelashes, though the degree of loss is highly variable. Chemotherapy is a systemic treatment designed to target rapidly dividing cells, the defining characteristic of cancer cells. Hair loss (alopecia) is a common side effect because the healthy cells that produce hair are also some of the fastest-growing cells in the body. This systemic effect means the treatment can impact hair follicles across the entire body, including those responsible for facial hair.
Understanding How Chemotherapy Causes Hair Loss
Chemotherapy drugs interfere with cell division, a process shared by tumor cells and certain healthy cells. Hair follicles contain matrix cells that divide rapidly to produce hair shafts, making them a primary target for chemotherapy agents. These agents cannot distinguish between a cancerous cell and a healthy, fast-growing hair cell.
The medications essentially damage the cells in the hair matrix, causing the hair shaft to narrow and break off, often at or near the skin’s surface. This process is known as anagen effluvium, where the follicle is prematurely forced out of the active growth (anagen) phase. Not all chemotherapy regimens cause hair loss; the extent depends on the specific drug, dosage, and frequency of treatment. Drugs like doxorubicin, paclitaxel, and docetaxel are commonly associated with significant hair loss across the entire body.
Why Eyebrows and Eyelashes May Be Affected Differently
The response of facial hair differs from scalp hair due to distinct growth cycles. Scalp hair spends up to 90% of its time in the active anagen growth phase, making it highly susceptible to drug damage. Eyebrows and eyelashes, in contrast, have a much shorter anagen phase and spend a greater proportion of time in the resting (telogen) phase.
Because more facial hair is already in a resting state, it is less vulnerable to the immediate effects of chemotherapy drugs. This difference often results in patients experiencing complete scalp hair loss but only thinning or partial loss of eyebrows and eyelashes. However, potent regimens, such as those involving taxane drugs like docetaxel, can still cause complete loss. Facial hair loss also commonly occurs later than scalp hair loss, sometimes even after the main treatment cycles have finished.
The Timeline of Loss and Recovery
The loss of eyebrows and eyelashes typically begins a few weeks after starting chemotherapy, often following the initial loss of scalp hair. This shedding usually starts around two to four weeks into the treatment course. The loss may occur gradually, presenting as thinning, or it can happen suddenly in clumps.
Since eyelashes serve a protective function for the eyes, their loss can sometimes lead to increased eye irritation or dryness, which can be managed with gentle eye drops. To manage the change in appearance, many turn to cosmetic solutions like eyebrow pencils, powders, or temporary brow tattoos. Practicing makeup techniques before hair loss begins can help a person feel more confident in maintaining their appearance throughout treatment.
Regrowth usually starts shortly after chemotherapy treatments have concluded. While scalp hair may begin to grow back within a few weeks, facial hair can sometimes take longer, with the first signs of growth appearing within six months. Full re-establishment of the hair may take up to a year, and the new hair may initially have a different texture or color. For the vast majority of patients, the loss is temporary, though some drugs, such as docetaxel, have been linked to persistent changes in rare cases.