Hair Loss After Radiotherapy: When It Starts and When the Hair Comes Back

Radiotherapy for breast cancer: does the hair on your head fall out?

Radiotherapy to the breast does not cause hair loss on the head. Radiotherapy acts exclusively in the area being treated, and the scalp lies outside that field. Cancer Research UK describes scalp hair loss in breast cancer only for cases in which the head is irradiated as well because of brain metastases.

Hair inside the radiation field itself can fall out. When the lymphatic drainage pathways are treated as well in breast cancer, this often affects the underarm hair on the treated side; the fine hair on the chest wall and upper chest can thin out too. These areas usually recover, because the dose reaching the follicle there is lower than during radiotherapy to the head.

The hair loss across the whole head that many breast cancer patients experience almost always comes from chemotherapy. Anyone receiving both treatments goes through them at different times and can easily attribute the loss to the wrong one. The section on radiotherapy and chemotherapy further down, including a comparison table, shows how to tell the two apart.

A third cause is often overlooked: endocrine therapy. In a case series of 112 patients reported in 2018 in the journal hautnah dermatologie, the thinning was attributable to aromatase inhibitors in 75 women and to tamoxifen in 37, and in more than 90 per cent of cases it was only mild. More on this in the article on hair loss caused by medication.

Common assumption: Every course of cancer radiotherapy causes hair loss. In fact: Only the hair that lies inside the radiation field falls out.

Common assumption: With breast cancer, radiotherapy makes the hair on your head fall out. In fact: Radiotherapy to the breast does not affect scalp hair; loss across the whole head almost always comes from chemotherapy given at the same time.

Why radiotherapy causes hair loss

Ionising radiation hits rapidly dividing cells hardest, and that includes the matrix cells of the hair follicle during the growth phase. The acute hair loss seen with radiotherapy is therefore called anagen effluvium: the hair breaks off or falls out inside the treated field, while the follicles outside the field remain untouched.

To reach the tumour, the beam passes through the scalp and the hair follicles located there. Even with carefully planned radiotherapy, this cannot be avoided entirely. The higher the dose arriving at the follicle and the larger the field, the greater the risk of hair loss.

This has to be distinguished from telogen effluvium: a diffuse hair loss that only sets in weeks after a trigger such as a serious illness or surgery and affects the whole head. The two forms are tied to different phases of the hair cycle, which explains why they run such different courses.

The radiotherapy itself follows the treatment plan drawn up by the radiotherapy team. Hair loss is a side effect that resolves in many cases, and it is no reason to skip a session or postpone treatment. If the hair loss is weighing on you, bring it up with your treatment team.

Hair loss after radiotherapy to the head: only inside the treated field

Hair loss after radiotherapy to the head almost always affects exactly the treated area, not the whole head. The typical pattern is circumscribed, often roundish, with a blurred edge. Diffuse loss across the entire scalp is rare with radiotherapy to the head alone.

What surprises many people: the hair often falls out on the opposite side as well, where the beam exits the head. Cancer Research UK describes this exit point explicitly, and Macmillan Cancer Support names both the entry and the exit area of the beam as affected.

The whole head is only affected if the field covers it, that is, with whole-brain radiotherapy or with total body irradiation before a stem cell transplant. The American Cancer Society notes that nearly all patients receiving external beam radiotherapy to the head, neck or central nervous system experience hair loss.

If loss does occur across the entire head, neither the radiotherapy nor the psychological strain is usually responsible. The cause is most often chemotherapy given at the same time, and less often telogen effluvium after a serious illness or surgery. For help telling the patterns apart, see the article on diffuse hair loss.

What happens to eyebrows and eyelashes?

Eyebrows and eyelashes only fall out during radiotherapy if they lie inside the radiation field. In practice this only happens with radiotherapy to the head and neck region, when the field reaches close to the face; the American Cancer Society lists head, neck and central nervous system radiotherapy as the situations in which hair loss occurs almost as a rule. With radiotherapy to the breast or the pelvis, brows and lashes are untouched.

If you lose scalp hair, eyebrows and eyelashes at the same time, that argues against radiotherapy as the cause. This pattern fits chemotherapy, which travels through the bloodstream and reaches every hair root in the growth phase, and not a locally confined treatment. If in doubt, ask your team which areas your radiation field actually covers.

The same logic applies to regrowth as on the head: at a lower dose inside the field the follicles are likely to recover, while at a high dose permanent loss is possible here too. The literature does not provide solid figures specifically for brows and lashes. Many people fill the gap cosmetically with an eyebrow pencil or stick-on eyebrows; on irritated skin inside the field, the same caution applies as with any other product.

What people typically report after radiotherapy to the head

Anyone looking for accounts of hair loss caused by radiotherapy to the head will find four observations that come up again and again and that are also documented in the patient information from Cancer Research UK and Macmillan: the bald patch at the exit point on the opposite side, the sharp edge between irradiated and non-irradiated hair, the changed texture of the regrowth, and a scalp that feels tight or burns even before the hair falls out.

You will find no invented personal accounts here, and that is deliberate. Anyone looking to connect with others going through the same thing can do so through psychosocial cancer counselling services and support groups; the social work team at the centre where you are treated, or a cancer charity, can point you to the ones near you.

Radiotherapy or chemotherapy: two different kinds of hair loss

Hair loss during radiotherapy and during chemotherapy arises in two different ways. Chemotherapy acts systemically through the bloodstream and reaches every hair root in the growth phase, while radiotherapy acts locally and only inside the treated field. This results in different patterns, different courses and different prospects for regrowth.

After chemotherapy, the hair virtually always comes back, usually within a few weeks to months after treatment ends and at first as fine fuzz. After radiotherapy, whether it returns depends on the dose, and regrowth tends to set in more slowly. The literature gives no reliable figures for how much more slowly.

Scalp cooling caps are of no help during radiotherapy. Their lack of effect has been published under the title “No prevention of radiotherapy-induced alopecia by scalp cooling” (PMID 26381532); with chemotherapy, by contrast, the effect is documented, in the HOPE trial among others. The reason lies in the mechanism: cooling reduces blood flow and thereby keeps the drug away from the follicle, and that offers no protection against ionising radiation.

How long does hair loss last after radiotherapy?

Hair loss after radiotherapy usually begins 2 to 3 weeks after the first session. This time frame is given consistently around the world, by Cancer Research UK, Macmillan Cancer Support, the American Cancer Society and the German Cancer Information Service at the DKFZ among others. Once the loss has begun, Macmillan says it takes about another week for the hair inside the field to fall out completely.

The literature does not name a precise low point. Clinically it falls towards the end of the course of radiotherapy or shortly afterwards, because the loss comes to a standstill once the radiotherapy ends. According to patient information, visible regrowth is to be expected roughly 3 to 6 months after treatment ends, as a guide value and not as a firm promise.

How long hair loss lasts after radiotherapy depends on several factors at once: on the dose arriving at the scalp, on the size of the field, on the fractionation schedule, on any concurrent chemotherapy and on any previous radiotherapy to the same region. Two people with the same diagnosis can therefore experience very different courses.

Does hair grow back after radiotherapy?

In most cases yes: the hair grows back after radiotherapy once treatment is complete, although more slowly than after chemotherapy. How completely depends above all on the dose that reached the follicles inside the field.

It can take weeks to months after radiotherapy before the first hairs become visible on bald or heavily thinned areas. With chemotherapy, fine fuzz often appears shortly after the drugs are stopped. With shorter, lower-dose radiotherapy, the hair roots usually recover on their own.

The regrowing hair can change. Macmillan Cancer Support mentions thinner, uneven hair and a different colour, and the American Cancer Society additionally mentions a changed texture, straight instead of curly for example. How pronounced this is varies from person to person; the literature gives no figure for how often it happens. In many cases the hair evens out again over the following months.

There is no documented number of weeks after which regrown hair may be coloured or toned again. As a rule of thumb: only once the skin reaction on the scalp has healed completely and after checking with your treatment team, because freshly regrown hair and irradiated skin can react more sensitively.

If nothing grows back after 6 to 12 months, this should be assessed by your radiotherapy team and a dermatologist. Behind it can lie permanent radiation-induced alopecia, in which the follicles inside the field have been destroyed. What tips the balance is explained in the next section.

Temporary or permanent: the role of the radiation dose

Whether the hair comes back is decided above all by the radiation dose that reached the scalp. Below certain thresholds the follicles usually recover, and as the dose rises the risk of permanent alopecia increases. The published threshold values, however, differ widely depending on the study, the technique and the patient group.

Writing in the International Journal of Radiation Oncology, Biology, Physics in 2004, Lawenda and colleagues reported a cumulative follicle dose of about 43 Gy at which half of the patients developed permanent alopecia. Phillips and colleagues, writing in JAMA Dermatology in 2020, placed temporary loss at around 20 Gy and above, and permanent loss rather above 30 to 36 Gy mean dose.

A prospective study by Jia-Mahasap and colleagues (2024) found thresholds for the scalp as a whole of around 22 Gy for temporary and around 37 Gy for permanent loss, each as a D2 value and assessed after six months. These figures are reference points from individual cohorts and not a universally valid limit for the individual case.

In technical terms, two processes exist side by side. In temporary alopecia the follicle survives and merely pauses its growth phase. In permanent, scarring radiation-induced alopecia the follicle is destroyed: studies of irradiated skin describe a thinned epidermis, atrophied follicles, denser collagen and a reduced blood supply. This is the same underlying process as in scarring hair loss.

So radiotherapy to the head does not automatically leave the scalp free of scarring. The risk rises further with repeat radiotherapy to the same field, with very large fields and with concurrent chemotherapy: in the paediatric group in Phillips (2020), the threshold for permanent loss under combination therapy was already around 21 Gy. Pre-existing hereditary hair loss is likely to overlay the picture further, although the dose studies do not document this.

Scalp care during radiotherapy

An irradiated scalp is more sensitive than healthy skin. Gentle cleansing, consistent sun protection and as little mechanical irritation as possible are what you can do yourself during radiotherapy. The instructions from your radiotherapy team always take priority, because the skin markings and the hospital’s own rules come into play there as well.

Specialist articles on preventing radiation dermatitis, including reports from the German Society of Radiation Oncology (DEGRO), recommend pH-neutral cleansing products free of fragrances and irritants as well as urea-based creams for care. Powder is advised against, because it dries the skin out further.

Once the hair inside the field falls out, the scalp loses its natural UV protection. The Spanish cancer society AECC points out explicitly that the scalp is then no longer protected from the sun and should be covered. Which products are suitable on irradiated skin is something to clarify with your treatment team.

With head coverings, the material makes the difference. Smooth cotton, silk, modal and bamboo viscose are soft and breathable; they sit comfortably without scratching and do not trap heat. Avoid coarse wool, stiff inner seams, labels at the neck and tight bands, because pressure and chafing inside the treated field intensify the skin reaction, something the DEGRO recommendations warn about explicitly.

A scalp that feels tight, burns or is tender to pressure, often even before the hair falls out, is a known side effect and is described as radiation dermatitis. That is not unusual and is no sign that anything has gone wrong. Redness, itching and flaking should still be brought up rather than treated on your own.

There is no universal rule about wearing a wig during the radiotherapy session itself. With radiotherapy to the head using an immobilisation mask there is usually no room for one anyway, and material on the skin can increase the skin dose, an effect described for thermoplastic masks. As a rule, no wig is worn during the session; what applies in your case is something your team on site will tell you.

Wigs and hair prostheses: sorting out who pays

When hair loss is caused by illness, a hair prosthesis is a reimbursable benefit in many countries. How much is covered differs from country to country, and often from region to region as well. In the UK a wig or hair prosthesis is usually arranged through the hospital treating you; for certain groups of patients it is free of charge, otherwise set charges apply, and the arrangements differ between England, Scotland, Wales and Northern Ireland.

The practical route is much the same everywhere: get written confirmation of the medical need from your doctor, and do it early. Clarify who covers the cost before you buy, not afterwards, and have the paperwork drawn up accordingly. You can get binding information from the team treating you at the hospital, from the patient support at your cancer centre or from the service that arranges hair prostheses there.

In practical terms, an early appointment pays off: ideally get it arranged and fitted before the hair falls out, while your own colour and volume can still serve as a template. Several European cancer societies give this same advice. During the treatment period a hair prosthesis is often the simplest solution, because nothing about the scalp itself has to change.

For many people, visible hair loss is the most distressing part of treatment. There are places to turn to for this: cancer information services and cancer charities keep directories of psychosocial cancer counselling services, whose counselling is usually free of charge. Cancer centres additionally offer psycho-oncological support.

Hair transplant after radiotherapy: what is realistically possible

After radiotherapy, a hair transplant can only be considered once the oncological treatment is complete, the scalp has healed stably and the doctors treating you have given their approval. And on irradiated skin, the starting conditions are worse than on a healthy scalp.

The reason lies in the tissue. Studies of irradiated skin describe a thinned epidermis, denser collagen, atrophied hair follicles and a reduced blood supply. That blood supply is exactly what transplanted follicles need in order to take. In the professional forum of the International Society of Hair Restoration Surgery, transplantation on irradiated scalp is accordingly listed among the difficult cases.

On timing: treatment completed, a stable situation and no repeat radiotherapy planned for the same region. Freshly transplanted follicles would not survive renewed radiotherapy in the same field. How long the interval has to be is decided by oncology, not by the wish for denser hair.

Whether a transplant is possible at all, and to what extent, is decided by a medical examination in each individual case. With extensive fibrosis the achievable result can be limited; sometimes several smaller sessions or a lower density are the more realistic plan. In methodological terms, the starting situation resembles a hair transplant on scars.

That also includes an honest no: after high-dose radiotherapy, the tissue can be so severely damaged that a transplant is out of the question. In that case a medical hair prosthesis is the solution that holds up permanently, and it is not a step backwards. With an irradiated scalp, no one can responsibly promise you in advance that a procedure will succeed.

Before any of this comes the question of what kind of hair loss is actually present: a radiation effect inside the field, a temporary effluvium after a serious illness, or an unrelated hereditary hair loss that happens to be progressing at the same time. A hair analysis classifies the pattern visually and is therefore one step towards clarity, not a finding and no substitute for a medical assessment.

With an irradiated scalp, this classification has a clear limit: radiation-induced fibrosis cannot be seen in photos. Whether the scalp meets the requirements for a procedure is only shown by an examination in person, with palpation of the skin and assessment of the blood supply, and exclusively after clearance from the oncologists treating you. The visual analysis therefore only answers the preliminary question of which hair loss pattern is present in the first place.

The free hair analysis classifies your hair visually. It does not assess an irradiated scalp, does not provide a diagnosis and replaces neither the conversation with your oncology team nor an examination in person.

When hair loss is temporary and when to have it assessed by a doctor

Whether hair loss after radiotherapy remains temporary depends on the radiation dose and the duration of treatment. With shorter, lower-dose courses the hair roots usually recover on their own, and it is not unusual for hair that had already been given up for lost to grow back around six months after treatment ends without any further intervention.

And this is not limited to radiotherapy for brain tumours. Hair loss on the head can occur with any radiotherapy in which the scalp lies in the beam path: with brain tumours and brain metastases, with head and neck tumours, with skin tumours of the scalp, with whole-brain radiotherapy and with total body irradiation before a stem cell transplant.

Patience is the right approach in the first months, because the follicles need time to recover. There are four situations in which that does not apply. In those cases you should have the hair loss assessed medically, by your radiotherapy team or by a dermatologist.

Hair loss after radiotherapy: your next steps

When it comes to hair loss after radiotherapy, there are six things you can take into your own hands, wherever you currently are in your treatment. The order follows the timeline, from the planning consultation to follow-up care.

A hair transplant is only worth discussing once the oncological treatment is complete, the scalp has healed stably and a doctor has given clearance, and even then only after an examination in person. Until then the question stays open, and with an irradiated scalp that is the more honest answer than any promise.

Frequently asked questions about hair loss after radiotherapy