What Happens to Your Scalp During Glioblastoma Radiation
Radiation therapy is a core part of standard glioblastoma care. For most newly diagnosed patients, it involves daily sessions five days a week for six weeks. Doctors usually combine this with temozolomide chemotherapy, a regimen called the Stupp protocol.
During each session, high-energy X-rays pass through the scalp on their way to the tumor. The tumor is the target. But the skin and hair follicles in the radiation field also absorb energy. This causes two of the most common side effects: scalp irritation (radiation dermatitis) and hair loss (radiation-induced alopecia).
Understanding why these changes happen and what you can do about them helps you manage them better and stay on schedule with treatment.
The Biology Behind the Burn
Radiation damages DNA in every cell it passes through. Cancer cells are the main target because they divide quickly and cannot repair radiation damage as well as healthy cells. But the scalp's outer skin layer and hair follicles also divide rapidly, making them vulnerable.
When radiation hits the hair follicle bulb at the base of each follicle, it disrupts the normal growth cycle. This triggers anagen effluvium, a sudden shedding of hair in the growth phase. Radiation can also injure the stem cells higher in the follicle, in a region called the bulge. Your body cannot easily repair damage to those stem cells. This is why some hair loss from cranial radiation becomes permanent in areas that got the highest doses.
Skin cells respond to radiation by triggering inflammation. Tiny blood vessels in the dermis expand. Immune cells flood the area. The outer skin barrier weakens. This is why your scalp feels hot, tight, and sometimes painful. Your skin is responding the way tissue responds to a burn.
Radiation Dermatitis: What You Will Likely See and Feel
Skin reactions during cranial radiation tend to follow a predictable pattern. Most patients notice changes in the second or third week of treatment. The National Brain Tumor Society explains that scalp skin irritation is one of the most commonly reported side effects for people receiving brain tumor radiotherapy.
Doctors grade skin reactions on a scale from 1 to 4. Most glioblastoma patients experience grade 1 or grade 2 reactions:
- Grade 1 (mild): Faint redness, mild warmth, slight dryness. The scalp looks flushed, like a mild sunburn.
- Grade 2 (moderate): Deeper redness, dry peeling, tenderness. Some patients develop small moist patches where the skin leaks fluid.
- Grade 3 (severe): Moist desquamation. Open, weeping skin sores beyond small skin folds. This may require a temporary break in treatment.
- Grade 4 (rare): Skin breakdown reaching deeper tissue layers. Requires immediate medical attention.
Reactions usually peak at the end of treatment or in the week after. They then begin to resolve over four to six weeks. Some dryness and skin discoloration may persist longer, especially in high-dose areas.
Hair Loss During Glioblastoma Radiation: Transient vs. Persistent Alopecia
Almost everyone receiving cranial radiation for glioblastoma loses hair in the treated field. The key question is whether that loss will be temporary or permanent. The answer depends largely on the total radiation dose that specific areas of your scalp receive.
A prospective study on scalp dose thresholds and alopecia published in PMC found that temporary hair loss was associated with scalp doses around 22 Gy, while permanent hair loss became more likely at doses approaching 37 Gy across the overall scalp region. At localized peak-dose areas, those thresholds were higher.
Research on persistent radiation-induced alopecia in PMC defined the condition as incomplete hair regrowth six months after radiotherapy. That study found that about 60 percent of cranial radiotherapy recipients developed persistent alopecia, with glioblastoma among the most common diagnoses in the group.
The standard glioblastoma radiation course delivers 60 Gy over six weeks to the tumor and surrounding tissue. Scalp tissue over the treatment area gets those doses. This means hair loss in those areas may be long-lasting or permanent, while hair outside the treatment area usually grows back.
Hair loss from radiation is also different from chemotherapy hair loss. Temozolomide, the chemotherapy used with radiation for glioblastoma, causes much milder hair thinning than many other chemotherapy drugs. Most of the scalp hair loss you experience during treatment comes from radiation, not temozolomide.
What to Expect Week by Week
Scalp changes happen gradually. Individual experiences vary, but here is a general timeline:
- Weeks 1–2: Mild scalp sensitivity and early redness. Some hair shedding may begin.
- Weeks 3–4: More visible hair loss within the treatment field. Skin redness deepens. Possible dryness or flaking.
- Weeks 5–6: Peak skin irritation. Hair loss is most visible. Mild moist patches may appear.
- Weeks 7–10 (post-treatment): Skin reactions begin to resolve. Some continued shedding may occur before regrowth starts.
- Months 2–4: Hair regrowth often begins in areas that received lower cumulative doses.
Day-by-Day Scalp Care During Treatment
Gentle scalp care during radiation can reduce the severity of your skin reaction and keep you comfortable. Memorial Sloan Kettering Cancer Center's radiation skin care guidelines offer practical advice for patients receiving cranial radiotherapy. Most radiation oncology teams follow similar principles:
- Wash gently and regularly. Shower or bathe daily with warm water, not hot. Use a mild, fragrance-free, hypoallergenic shampoo. Do not scrub the scalp.
- Pat dry, never rub. Use a soft towel and press it gently against the scalp. Rubbing adds friction that worsens irritation.
- Apply a moisturizer from day one. Use a fragrance-free, non-medicated moisturizer twice daily starting at the beginning of treatment. Ask your radiation nurse which products your center recommends. Common options are aloe gels or simple barrier creams.
- Use a soft-bristle brush or wide-tooth comb only. These are gentler on skin that is already under stress.
- Avoid heat styling tools. Blow dryers, curling irons, and flat irons add thermal stress to compromised skin. Let hair air dry instead.
- Protect the scalp outdoors. Wear a hat, soft scarf, or head covering when outside. The treated scalp burns more easily than untreated skin. On any exposed area, use SPF 30 or higher, PABA-free sunscreen.
- Sleep on soft fabrics. Satin or cotton pillowcases reduce nighttime friction against the scalp.
The National Brain Tumor Society's tips for managing radiation side effects also stress the importance of staying in close communication with your radiation oncology team. Call about small but worsening changes in your scalp. Don't wait until your next appointment.
What to Avoid During and After Radiation
Several common products and habits can worsen scalp reactions. Avoid the following during treatment and for several weeks afterward:
- Hair dyes, bleaches, chemical relaxers, or perms
- Products containing alcohol, fragrances, or menthol
- Tight hats, headbands, or anything that applies sustained pressure to the treatment area
- Scratching or picking at dry or peeling skin. This breaks the skin barrier and raises infection risk.
- Swimming in chlorinated pools or the ocean
- Direct sun exposure to the treated scalp without a physical barrier or sunscreen
- Over-the-counter steroid creams or antibiotic ointments applied without your care team's guidance
When Hair Grows Back — and When It May Not
For areas that got lower doses, hair usually starts growing back two to four months after treatment ends. For areas directly over the tumor field where doses were highest, recovery depends on how much stem cell damage occurred in the follicle bulge.
Research on persistent radiation-induced alopecia showed that minoxidil cream helped about 82 percent of patients with incomplete regrowth. Doctors can offer surgery for patients it doesn't help. Talk to your cancer team about these options in the context of your overall treatment status.
Ask your radiation oncologist before treatment begins which parts of your scalp will get the highest doses. This helps you know which areas might grow hair back and which might not.
Scalp-Sparing Radiation: An Evolving Option Worth Asking About
One newer approach is scalp-sparing radiation planning. This method delivers the full dose to the tumor while keeping scalp doses as low as possible.
The SPARE trial (Scalp-Sparing Radiation With Concurrent Temozolomide and Tumor Treating Fields) studied this approach in newly diagnosed glioblastoma patients receiving standard chemoradiation alongside TTFields. Early results showed this method may reduce skin damage and hair loss without affecting tumor control. But more research is needed.
Not all hospitals offer this, and it requires special planning equipment. If you want to reduce hair loss and skin damage, ask your doctor if your hospital can do this and if your tumor's location allows it. For more on TTFields, which is a device worn on the scalp during and after radiation with its own skin considerations, see our article on Tumor Treating Fields for Glioblastoma: How the Optune Device Works, Who Qualifies, and What to Expect.
Emotional and Practical Dimensions of Hair Loss
Hair loss can be emotionally hard. For some patients and families, it's the first visible sign of cancer treatment. It's okay to feel upset about it. Your care team should take these feelings seriously.
Several practical steps can help:
- Cut your hair short before treatment starts. This makes shedding less noticeable.
- Ask about wigs and head coverings. Many hospitals have programs to provide them for free.
- Talk to your social worker or care team if hair loss is really bothering you. Your team is ready to help.
If you are newly diagnosed and preparing to begin radiation, our overview of what to expect in the first 30 days after a glioblastoma diagnosis may help you prepare for the broader treatment experience alongside these scalp-related changes.
Radiation's Effects Beyond the Scalp: A Brief Note
Radiation affects the scalp, but it can also affect brain tissue. Changes may happen weeks or months after treatment ends. If you notice new or worse symptoms after finishing radiation, discuss them with your oncologist promptly. These could be from tumor growth, treatment response, or radiation necrosis. For more on telling radiation effects apart from actual tumor regrowth, see our article on Radiation Necrosis After Glioblastoma Treatment: How to Tell It Apart From Tumor Recurrence.
When to Talk to Your Doctor
Contact your radiation oncology team if you notice any of the following during or after treatment:
- Open sores, blisters, or areas of moist weeping skin on the scalp
- Signs of infection: increasing warmth, pus, expanding redness, or fever
- Severe scalp pain that standard comfort measures are not managing
- Skin changes spreading beyond the radiation treatment area
- Hair loss or scalp changes that concern you and have not been discussed with your team
Call your radiation nurse with skin concerns between visits. Call early. Early treatment works better.
This article is for general information and is not a substitute for medical advice. Always consult your oncologist or care team about your specific situation.