You have been given your treatment schedule, you read “alopecia” in the list of side effects, and you opened a browser to find out what to use. Or you are already two weeks past the first infusion, your scalp has started to hurt, and hair comes away with the lightest pull.
The short answer is uncomfortable: there is no shampoo, ampoule, oil, vitamin or salon treatment that prevents chemotherapy-induced hair loss. Anyone selling you that is selling hope.
The long answer is more useful, because there is plenty left to do. It is just somewhere else: not in the hair, but in the skin underneath it.
The hair does not fall from the root, it breaks
In the kind of shedding most women know (after childbirth, after an aggressive diet, after an infection), the follicle goes into a resting phase and the whole hair is released, bulb and all. That takes two to three months to become visible.
Chemotherapy does something different. Chemotherapy drugs act on rapidly dividing cells, and the follicle matrix, the factory that pushes the hair outward, is one of the fastest-dividing tissues in the human body. At any given moment, eight or nine out of every ten scalp follicles are in an active growth phase. All of them are hit at once.
The result is that the hair shaft becomes thin and fragile at one specific point, and breaks there. That is why chemotherapy hair loss starts early, between two and four weeks after the first cycle, and that is why it is so fast: it is not one hair releasing at a time, it is an entire crop failing together.
Two practical consequences. First: the window between the infusion and the shedding is short, so it is worth deciding in advance what you want to do, rather than in a panic. Second: because the problem is shaft breakage, anything that adds tension (hard brushing, tight elastics, pulled-back styles, hair twisted in a towel) speeds up the mechanical part, even if it does nothing to the chemical part.
It depends far more on the drug than on you
Not every cancer treatment causes hair loss, and the ones that do don’t all do it the same way. Anthracyclines, taxanes and cyclophosphamide, used in several breast cancer regimens, are among those with the highest incidence. Other protocols cause mild thinning, or nothing noticeable.
Endocrine therapy is a separate subject: tamoxifen and aromatase inhibitors do not usually cause total loss, but they can cause diffuse thinning that sets in slowly and lasts for years. Many women get through chemotherapy, see their hair come back, and a year later notice it is finer. That is not the same phenomenon and it is not solved by the same reasoning.
Ask your oncologist, in these words: does my regimen usually cause hair loss? That one question is worth more than twenty websites.
What actually changes how much you lose
| What you hear | What is known today | Who decides |
|---|---|---|
| Scalp cooling (a cold cap worn during the infusion) | The only intervention with reasonable evidence of reducing hair loss. It reduces, it does not eliminate, and it works better with some regimens than others. It is not indicated in every type of cancer, including blood cancers | The oncology team, and it depends on the clinic offering it |
| “Anti-hair-loss” shampoo, ampoule, tonic or oil | They do not act on the matrix the drug is hitting. There is no way for a cosmetic to shield the very cell the treatment is targeting | Nobody needs to decide, there is nothing to decide |
| Minoxidil | It does not prevent the loss. It has been studied as a way to shorten recovery time afterwards, with modest results, and it is a medication | A doctor, never the salon |
| Biotin, collagen or vitamin supplements | There is no biological reason to expect an effect here, and supplements can interfere with test results or with treatment | The oncology team |
| Massage, laser, microneedling, anything that pierces, scrapes or exfoliates | Out of the question during treatment. With altered immunity and platelet counts, a small injury to the scalp is an entry point for infection and can bleed more than it should | The oncology team, and the usual answer is no |
What is left is the skin, and the skin needs work
With hair thinned out or gone, the scalp becomes exposed skin, and skin that is already more sensitive because of treatment. This is the part you control.
Sun protection, every day. An uncovered scalp burns easily, and a burn on sensitised skin hurts and flakes for days. Sunscreen over the whole head, including the nape and the ears, plus a hat or a scarf when you are genuinely out in the sun. In São Paulo this matters all year, not only in summer.
Yes, wash it. There is an idea going around that you should not wash your hair during chemotherapy. Not washing holds on to exactly zero hairs and leaves oil, sweat and flaking piled up on skin that is already irritated. Use warm water rather than hot, a gentle shampoo, and massage with the pads of your fingers, no nails. Every two or three days is reasonable when there is little hair left to get dirty.
Friction. A silk or satin pillowcase, a towel pressed rather than twisted, a soft cotton cap for sleeping. None of this keeps hair on your head, but all of it avoids breaking early what is still there.
Dryness and itching. A dry, sensitive scalp during treatment is common. A light, fragrance-free moisturiser helps. Burning, stabbing pain or tenderness to the touch during the shedding days are also reported often, and they tend to settle once the shedding is complete.
Cutting it first. Cutting your hair very short before the shedding starts does not make it grow back stronger, and anyone who tells you otherwise is wrong. What the cut does is practical: less weight, less tension, easier hygiene, and a less brutal process to watch. If you are considering a wig or hairpiece, measure and choose before you lose your hair, while the colour and density are still in front of you.
Chemical services, only afterwards, and slowly
During treatment, colour, bleach, straightening and perms are off the table. The scalp is more permeable and more reactive, the skin barrier is in worse shape, and there is no benefit that justifies the risk of dermatitis or a chemical burn at a moment when immunity is low.
Afterwards, the hair that grows is new hair, with a still-immature cuticle, and it behaves differently from the hair you had. The practical rule used in many services is to wait for the new hair to gain some length, a few months after treatment ends, and to start with the gentlest options, with a strand test before anything is applied on the scalp. Your oncologist decides the timing.
What to expect when your hair comes back
In most cases, the follicle resumes production after treatment ends, with the first signs between one and three months. The new hair usually comes in different for a while: finer, sometimes wavier, sometimes darker or greyer. That tends to even out over the following cycles, but it may not go back to exactly what it was.
There is also persistent alopecia after chemotherapy, where density does not return to its previous level. It is a minority of cases, estimates vary quite a lot between studies, and it shows up more often in connection with certain drugs, taxanes among them. If six months to a year after the end of treatment there are areas where nothing has grown back, that is an appointment with a dermatologist, not with a salon.
When it is not a salon matter
Contact your medical team, not a beauty professional, if any of this appears: an open sore, crust, pus, blister or bleeding on the scalp; pain that does not improve and does not track the shedding phase; a patch of reddened, flaking or hardened skin; a fever at any point during treatment. During chemotherapy, a scalp infection is urgent and does not wait.
And if the shedding did not begin with treatment, or carried on for months after it, there may be other causes running alongside, from anaemia and thyroid problems to an androgenetic pattern that was already setting in. That is investigated with blood tests and a doctor.
If you would like to talk about your case
Nelblack is in Tatuapé, in the East Zone of São Paulo, close to the Carrão and Tatuapé metro stations. We are open Tuesday to Saturday, 9am to 6pm, by appointment, and Tuesday is the day reserved for scalp therapy. We can see you in English.
The trichoscope hair assessment costs R$200 (Brazilian reais), credited in full towards the protocol if you decide to go ahead. It is magnified imaging of the scalp and the hair, which you follow on screen together with Nelma Faleiro, a specialist in cosmetic trichology. You do not leave with paperwork: you leave having seen your own scalp and having talked through what was there.
It is worth being clear about when it helps. During chemotherapy, the assessment is there to record your starting point and to guide the care of the scalp skin, not to begin a protocol. Any procedure depends on clearance from your oncologist, and we ask for that before we touch you. After treatment, with your hair coming back, trichoscopy becomes useful in a different way: we can measure density and thickness, repeat the measurement over the months, and tell apart what is growing from what is not.
When a protocol is under way, the number of sessions depends on what the scalp and hair need, and we measure again during or at the last session to compare with the image from the first day, at no extra cost. We would rather show you the measurement than sell sessions on impression.