What grows back and what doesn’t

You’ve lost a lot of hair over the past few months. The shedding is slowing down, or not yet. And one question keeps going round in your head: will it come back? The answer depends on a tiny structure you can’t see, the follicle. In most cases, it leans towards yes.

It all depends on the follicle

Every hair grows out of a follicle, a small pocket under the skin that makes it. The hair itself is replaceable: it falls out at the end of its cycle and a new one grows in the same place. What matters is that the follicle is still there.

So dermatologists sort hair loss into two families. In non-scarring hair loss, by far the most common, the follicle isn’t destroyed: even while resting, it can still make a new hair¹. In scarring hair loss, it’s destroyed for good and replaced by fibrous tissue, like a scar: hair can no longer grow back in that spot¹.

In between sits pattern hair loss, where the follicle doesn’t die all at once but shrinks year after year. More on that below.

After a fever, childbirth or a shock

This is the most common type when hair comes out in handfuls. It’s called telogen effluvium. Something disrupts the hair cycle (giving birth, a high fever, an emotional shock) and a lot of hairs switch to their resting phase at the same time. They fall out two to three months later¹.

Here, regrowth is the rule. The British Association of Dermatologists (BAD) puts it plainly: telogen effluvium usually gets completely better without any treatment. The shedding phase lasts 3 to 6 months, then new hair starts to grow². Once the shedding stops, most people see their hair regain its normal fullness within 6 to 9 months³.

Two caveats. If the cause carries on, such as iron deficiency that’s never treated, the shedding can come back. And when it lasts more than six months, it’s called chronic telogen effluvium², which is worth a doctor’s opinion.

Testimonials posted on the HairLossTalk forum¹²¹³.

Two very different paces: three months for one, several years of ups and downs for the other. In both cases, the hair came back.

Alopecia areata

Alopecia areata makes hair fall out in round, smooth patches, often about the size of a coin. The immune system attacks the follicle and stops it from making hair⁵. It’s alarming, but the roots aren’t destroyed: the hair can grow back⁵.

According to the BAD, four in five people affected get complete regrowth within a year without treatment, with the odds depending on how much hair is lost. When more than half the hair goes at the start, or with complete hair loss at any stage, the chance of full recovery drops to about one in ten⁵. Regrowth usually starts in the centre of the patch, with fine white hairs that thicken and then get their colour back⁵.

It can also return: most people have further episodes⁵. An Italian team contacted 191 patients 15 to 22 years after their diagnosis: 66 were completely free of the condition. The factor most linked to how it played out was how severe it was at the first consultation⁶. A limitation the authors point out themselves: follow-up was done by phone only, with no examination⁶.

Hairstyles that pull

A tight bun, braids, extensions worn for years: repeated pulling eventually damages the hair along the forehead and temples. This is traction alopecia. At first, it doesn’t scar. If the tension continues, the follicles end up destroyed and the loss becomes permanent⁷. The American Academy of Dermatology (AAD) sums it up: the longer it goes untreated, the more likely it is to be permanent⁸.

The first signs show along the hairline: short broken hairs, a receding hairline, thinner patches where the hair is pulled tight⁸. What matters is to loosen the hairstyle as soon as you notice them⁸.

Pattern hair loss

Pattern hair loss, or androgenetic alopecia, follows a different logic. Driven by genetics and hormones, the follicles gradually shrink: hairs get finer and sparser, and some end up as barely visible fuzz⁹. It progresses slowly, over years or even decades, and eventually the worst-affected follicles stop producing hair¹⁰. In women, it mostly thins the top of the head and widens the parting, while the front hairline stays⁹.

Treatments can stop or slow the loss, and sometimes bring partial regrowth⁹. They work for as long as you use them: stop, and the hair loss picks up where it left off⁹. The AAD adds that the earlier treatment starts, the better it works³. Your doctor can suggest a treatment suited to your stage.

Hair loss that leaves a scar

Less common, scarring alopecias include several inflammatory scalp conditions, such as lichen planopilaris and frontal fibrosing alopecia⁴. They show up as bald patches with no visible follicle openings⁴. They can itch, burn or hurt, but not always; at the edges of the patches, the skin is often red and scaly around each hair¹¹.

Hair lost in those areas doesn’t come back⁴. Treatment aims to slow the disease and ease the symptoms¹¹, which is why the French Society of Dermatology (SFD) stresses prompt medical care¹. A patch that’s spreading, or skin that’s red or sore, is a reason to see a doctor without waiting.

How long to wait

Even when everything grows back, it takes patience. A hair grows about 1 cm a month⁴. A hair that restarts in January is barely 3 cm long by April: it’s there, but it still gets lost in your hairstyle.

• After telogen effluvium: the shedding lasts 3 to 6 months², then fullness returns within 6 to 9 months³.
• With alopecia areata: regrowth happens over months, rarely over years⁵.
• With treated pattern hair loss: the effect on shedding is judged at around 3 months, regrowth takes at least 6 months, and the maximum effect usually comes at around a year⁹.

Judge too early and you’ll often wrongly conclude that nothing is happening.

Watching the regrowth come in

One centimetre a month doesn’t show from one day to the next. In the mirror, the light changes, the angle changes, and worry does the rest. You see the shedding everywhere and the regrowth nowhere.

The most reliable way is the same photo every week, in the same conditions. Calvap helps with that: last week’s photo appears as a see-through overlay, so you can line up the same framing in a few seconds, across seven areas of the scalp. Aim for the parting, the crown and the temples, where small regrowing hairs often show first. Note what you change in the journal too, like a treatment you’ve started.

After a few months, you compare two dates and see whether the parting is narrowing and the patches are filling in. And if you see a doctor, you bring dated photos rather than an impression.