You were parting your hair, or somebody standing behind you said something. A bald patch the size of a coin, smooth and round, with skin that looks perfectly normal inside it: not red, not flaking, not itchy, not sore. Last week there was nothing there.
The first reaction is almost always the same. It must be stress, it must be the dye, and it will probably grow back on its own. So in come the ampoule, the tonic and the oil your cousin swears by, and three months go past.
This picture has a name, and that name changes what you should be doing next week.
The shape of the patch says more than its size
A round or oval patch with a well-defined edge, appearing over a matter of weeks, with normal-looking skin inside it, is the classic presentation of alopecia areata: an autoimmune condition in which the body’s own defence cells attack the hair root and interrupt growth.
The important word there is autoimmune. It is not a nutritional gap, not the wrong product, not poor hygiene, not a fungus. It is the immune system treating the follicle as foreign.
The second important word is non-scarring. The follicle is interrupted, not destroyed. Look closely at the skin inside the patch and the follicular openings (the tiny dots where each hair comes out) are still there. That is the best news in this article: a follicle that still exists can go back to producing hair, even after months or years. In scarring alopecias the openings disappear and the skin goes smooth and shiny like a scar, because there is nothing left to recover.
Something in the region of 2% of people are thought to have an episode of alopecia areata at some point in life. It is not rare, and it is not only a childhood thing.
What else makes a roundish patch
| What you see | Most likely explanation | Who sorts it out |
|---|---|---|
| Smooth patch, crisp edge, normal skin, appeared within weeks | Alopecia areata | Dermatologist |
| Patch with flaking, broken stubs of hair, itching, sometimes reddened skin | Scalp ringworm (a fungal infection) | Dermatologist, with a mycology test |
| Patch containing hairs of different lengths, irregular outline, never completely bare | Trichotillomania (hair pulling, sometimes unconsciously) | Dermatologist plus psychological support |
| Thinning at the edges, hairline receding, built up over months of tightly pulled styles | Traction alopecia | Change of styling, scalp therapy, dermatologist if the loss is already fixed |
| Smooth, shiny skin with no follicular openings, or redness and scaling around each hair, with burning or pain | Scarring alopecia | Dermatologist, urgently |
None of those distinctions can be made from a description. All of them are made by looking at the skin up close.
The belief that costs you: “it is stress, it will grow back”
This is the part where I disagree with the common wisdom, so it is worth explaining why.
The belief is not entirely wrong. A good share of cases of one single small patch do fill back in within about a year with no treatment at all. That is true, and it is documented.
The problem lies elsewhere. “Wait and see” is a reasonable clinical decision, and it may well be what the dermatologist chooses for you. But it is reasonable after the diagnosis, not before. Waiting without knowing what you are waiting on is a different thing: you are betting on a favourable case of alopecia areata when it could be ringworm (which spreads and worsens without an antifungal) or a scarring alopecia (where every month of waiting costs follicles that do not come back).
And then there is timing within alopecia areata itself. The condition has active phases and quiet phases. Medications that act on the immune process tend to deliver more while the condition is active. Once a patch has been stable for a long time, the response is usually smaller. In other words, the window in which medical treatment works best is exactly the window you spend trying cosmetics.
Three months of ampoules are not neutral. They are three months.
It was not the dye, the braid, or something you did wrong
Worth saying plainly, because guilt comes up in almost every conversation on this subject.
Alopecia areata is not caused by colouring, by relaxers, by washing too little, by washing too much, by wearing a cap, or by a vitamin deficiency. Stress is described as a possible trigger in people who are predisposed, not as a cause, and plenty of people develop areata with no notable event behind it.
What does exist is genetic predisposition and an association with other autoimmune conditions. That is why dermatologists tend to investigate the thyroid, including TSH (thyroid-stimulating hormone) and antithyroid antibodies, and to ask about family history, vitiligo, rhinitis, asthma and atopic dermatitis.
It is also worth looking at your nails. Small pinpoint dents on the nail surface, like pinprick marks, show up in a proportion of cases and are a clue the doctor will use.
What a dermatologist has to work with
Not so that you can self-medicate, but so that you know there is a course of action, and that it is not “learn to live with it”.
For localised patches in an adult, the most commonly used first line is a corticosteroid injected into the lesion, repeated every few weeks. There is also high-potency topical corticosteroid, and minoxidil may come in as an adjunct, bearing in mind that it stimulates growth but does nothing to the autoimmune process. For extensive cases there is topical immunotherapy and, in recent years, oral medicines in the class of JAK inhibitors (JAK stands for Janus kinase, an enzyme involved in inflammatory signalling), approved for severe alopecia areata, including in Brazil by Anvisa, the national health surveillance agency. They require a prescription and mandatory monitoring tests.
None of that comes in a bottle off a cosmetics shelf. Which is why the route here is an appointment, not a shop.
See a dermatologist this month if
- The patch has a crisp edge and the skin inside it is smooth and shiny, with no
follicular openings.
- There is flaking, crusting, an open sore, pus, burning or pain.
- More than one patch has appeared, or the patch grew in under a month.
- The patch runs in a band along the hairline, behind the ears or at the nape.
- You are also losing eyelashes, eyebrows or body hair.
- It is a child. In children, scalp ringworm is a frequent cause and needs an
oral antifungal.
What trichoscopy adds, and what it does not replace
Trichoscopy is a magnified image of the scalp. In a scalp therapy studio it does three concrete things: it shows whether the follicular openings are preserved or lost, which is what separates a reversible picture from a scarring one; it measures density and thickness at the same points over time, so that progress is followed by numbers rather than by impressions; and it recognises patterns that call for a referral, including signs of activity at the edge of the patch, such as short hairs that taper towards the base.
What it does not do is diagnose. Diagnosing an autoimmune disease, a fungal infection or a scarring alopecia is a medical act, involving clinical examination, laboratory work and, where necessary, a biopsy. Any professional offering a protocol to “treat your areata” without a doctor involved is selling something they do not have.
What belongs outside the consulting room is the groundwork: managing any associated oiliness and flaking, suspending harsh chemical services in the area, reducing tension on the hair, and planning a cut that lives comfortably with the patch while treatment runs. That is support, not treatment of the cause.
What to do this week
Photograph the patch today, in good light, with a coin next to it for scale. Repeat the photo weekly, always in the same light. That sequence is worth more at the appointment than any description.
Book a dermatologist. If the wait is long, book anyway and take the photos with you.
Do not start a corticosteroid, an antifungal or any other medicine on your own, or on the recommendation of somebody who has been through it. A corticosteroid on a fungal infection makes things worse, and the two look alike enough to fool you.
If you would like to talk about your case
At Nelblack, in Tatuapé (São Paulo’s East Zone, near the Carrão and Tatuapé metro stations), the trichoscope hair assessment shows whether the follicular openings are preserved, measures density and thickness at the same points, and records the state of the scalp around the patch. You follow the trichoscopy on screen, alongside the professional, as the images come up. There is no report or paperwork handed over: it is a conversation with the measurements in front of you. If what shows up calls for a doctor, you leave knowing that, and knowing what to look at during the appointment.
It costs R$200, in Brazilian reais, credited in full towards the protocol. We measure the same points again during or at the last session and compare them with the image from the first day. At no extra cost.
We are open Tuesday to Saturday, 9am to 6pm, by appointment, and we serve clients in English. Tuesdays are the day reserved for scalp therapy. If you already have test results or notes from a dermatologist, bring them.