Brain radiation is a treatment that can cause hair loss. This therapy uses high-energy beams to target and destroy abnormal cells, such as those found in brain tumors or metastases. While the radiation is precisely aimed at the disease, it can affect healthy, rapidly dividing cells in the scalp, leading to hair shedding. This side effect, known as alopecia, is a concern for patients undergoing this treatment. The potential for hair loss is directly linked to the treatment area and the energy delivered, making it a highly localized effect that is different from the widespread hair loss seen with many chemotherapy drugs.
How Radiation Damages Hair Follicles
The mechanism by which radiation causes hair loss centers on its effect on cells that rapidly multiply. Hair follicles are among the most actively dividing tissues in the body, making them vulnerable to radiation damage. The matrix cells located in the hair bulb are responsible for producing the hair shaft during the growth phase.
When radiation beams pass through the scalp, they damage the DNA of these matrix cells, halting their rapid proliferation. This interruption prevents the hair follicle from forming a healthy, strong hair shaft. The affected hairs quickly stop growing and enter an abnormal resting phase. The hair sheds from the scalp approximately two to three weeks after the start of treatment. This hair loss is confined only to the area exposed to the radiation beam, which is why it is typically localized rather than total.
Dose and Location as Determinants of Loss
The severity and pattern of hair loss are influenced by the specific parameters of the radiation treatment. The total radiation dose delivered to the scalp is the primary factor determining whether the hair loss will be temporary or permanent. Higher doses of radiation are associated with more severe and potentially irreversible damage to the hair follicles and their stem cells.
Lower doses, such as a single fraction dose of less than 2 Gray (Gy), may only cause temporary thinning. Permanent hair loss becomes more likely when the hair follicles receive a total dose exceeding a specific threshold. These high doses can destroy the follicle’s stem cells, which are necessary for long-term hair regrowth.
The location of the radiation determines the exact pattern of hair loss on the scalp. Whole-brain radiation therapy, which treats the entire head, typically leads to widespread hair loss across the scalp. Conversely, highly targeted treatments, such as stereotactic radiation, only cause hair loss in the precise, small patch of the scalp where the radiation beams enter and exit the head.
Understanding Hair Regrowth and Permanent Alopecia
For patients who receive lower doses of radiation, the hair loss is often temporary, and regrowth can be expected. Hair regrowth typically begins within two to three months after the completion of treatment, with noticeable coverage occurring within three to six months.
When hair regrows after temporary loss, the new hair may have a different texture or color than the original hair, sometimes returning thinner or curlier. Permanent alopecia, or incomplete regrowth, is a risk directly tied to the total radiation dose delivered to the hair follicle. High doses can cause irreversible damage to the stem cells within the follicle, preventing future hair growth in the treated area.
Persistent radiation-induced alopecia is defined as incomplete hair regrowth after six months, and occurs in a percentage of patients who undergo cranial irradiation. If the damage is permanent, the hair loss will remain confined to the specific areas that received the high-dose radiation. Consulting with the oncology team before treatment can help establish realistic expectations about the likelihood of temporary versus permanent hair loss.
Practical Ways to Cope During Treatment
Patients can adopt several gentle hair care practices to manage the scalp during and immediately after radiation therapy. It is advisable to use mild, non-perfumed shampoos, such as baby shampoo, and to pat the hair dry with a soft towel rather than rubbing vigorously or using a blow dryer. Harsh styling methods, including perms, hair coloring, and heated tools like curling irons or straighteners, should be avoided as they can further damage the sensitive hair follicles and scalp.
Cutting the hair short before treatment begins can make the eventual hair shedding feel less dramatic and easier to manage. Many patients choose to cover their scalp with soft hats, scarves, turbans, or wigs to protect the skin and feel more comfortable. A sensitive scalp must be protected from the sun and cold, so head coverings or sunscreen should be used when outdoors.
For those planning to wear a wig, it can be helpful to select one before the hair loss starts to match the natural color and texture more easily. If the scalp becomes dry or itchy, a gentle, unperfumed moisturizer or emollient can provide relief. The oncology team or a specialized nurse can provide personalized recommendations and resources for coping with this side effect.