Hair loss in women: where it comes from

Your ponytail feels thinner than it used to. There’s more hair in your brush, in the drain, on your shoulders. You wonder if it’s stress, the pill, winter or something more serious. The American Academy of Dermatology actually lists a thinning ponytail among the signs worth paying attention to¹.

In women, hair loss has many causes, and most of them are harmless and temporary². The point is to tell apart the ones that go away on their own from the ones that need a doctor’s opinion.

How much shedding is normal

You lose between 50 and 100 hairs a day, often without noticing³. That’s normal turnover: a hair grows for years, rests for a few months, then falls out to make room for a new one⁴. On wash days you see more, simply because they all come out at once.

A handful one morning isn’t what should worry you. Shedding that goes on and on, or volume that drops month after month, is.

Temporary causes

Most sudden shedding works the same way: something pushes a lot of hairs into the resting phase at once. They then fall out together a few weeks later. Dermatologists call this telogen effluvium. It can affect up to half the hairs on your scalp⁴.

The catch is the delay. The hair falls out in large amounts two to three months after the trigger². So you look for the cause in the past week, when it actually happened last season. The most common triggers:

• the season: shedding is often heavier in spring and especially in autumn²;
• pregnancy and giving birth: shedding after the baby arrives is very common, and we cover it in a full article²;
• the pill: some can make shedding worse, others can improve it², and stopping a pill is a known trigger⁴;
• intense stress, such as a divorce or a death in the family, an illness or surgery⁵;
• weight loss or an unusual diet⁴.

Once the trigger has passed, most people get their volume back within 6 to 9 months⁵. Some women, though, keep shedding more than normal for a long time, sometimes for years. This is called chronic telogen effluvium⁴. That’s a reason to see a doctor.

What a blood test can look for

When there’s no obvious explanation, your doctor may order a blood test. The French Society of Dermatology (SFD) lists low iron, a thyroid problem, low vitamin D and B12 and hormonal problems².

Iron first. Iron deficiency is common in women and can cause diffuse shedding. It’s often linked to heavy periods, several pregnancies or a diet low in iron². Once your body gets back what it was missing, the hair can grow back⁵.

Then the thyroid. Whether it’s overactive or underactive, it can make your hair fall out². The topic has its traps, including a delay of several months: we explain them in our article on the thyroid.

Hormones too. Polycystic ovary syndrome (PCOS) can affect your hair². Acne, irregular periods or more hair on the face or body can point to it, but most women with PCOS don’t lose their hair⁶.

Finally, some medicines, for example for epilepsy or high blood pressure, can be the cause². Never stop a treatment on your own: talk to the doctor who prescribed it.

Female pattern hair loss

When those causes have been ruled out and the shedding sticks around, it may be androgenetic alopecia, or female pattern hair loss. It affects about one woman in five by age 40⁷. It’s largely inherited, and it can come from your mother’s side as well as your father’s⁷.

It doesn’t look like male pattern baldness. The hairline usually stays in place. The hair gets finer and sparser on top of the head, and a center part slowly gets wider. Complete loss is rare⁷. For most women it starts in their 40s, 50s or 60s, sometimes earlier, and becomes more common after menopause¹.

These figures come from a British study that examined women who were seeing a dermatologist for a completely different problem⁸. They were patients at a single hospital, not a sample of the whole population. A more recent Thai study found 52% among 178 postmenopausal women aged 50 to 65, using standardized photos and a close-up scalp exam⁹. The numbers depend on how you count, but the trend is the same: the older you get, the more common it is.

Temporary shedding or pattern hair loss?

At first, the two look alike. DermNet points out that chronic telogen effluvium is often mistaken for female pattern hair loss, even though they aren’t managed the same way⁶.

A few clues help. Telogen effluvium makes hair fall out all over the head, fairly suddenly, a few months after a trigger. Female pattern hair loss moves slowly and stays on top, around the part. The hairs there get finer: under magnification, they don’t all have the same thickness⁷.

Female pattern hair loss is mostly diagnosed by examining the scalp, and no test is routine when it looks typical. Hormone tests are sometimes ordered, for example if your periods are irregular⁷. The dermatologist may also gently pull on a small bunch of hair: if several hairs come out easily, the shedding is still active⁷.

What helps day to day

No product stops hair loss on its own. Some habits still avoid damaging hair that’s already fragile.

• Shampoo doesn’t make shedding worse, so keep washing your hair as usual. The SFD does say that no shampoo really stops hair loss⁷.
• Hold the hair dryer at a distance, and not on the hottest setting⁷.
• Avoid very tight hairstyles. Repeated pulling can cause permanent loss⁵.
• Space out coloring, perms and straightening: they can damage your hair⁵.
• Wear a cap in the sun if you like: a hat or helmet doesn’t make pattern hair loss worse⁷.

When to see a doctor

With female pattern hair loss, seeing someone early really matters. Without treatment it tends to progress, and treatment works best when it starts at the first signs¹. Your doctor can suggest a treatment that fits your situation. The NHS warns that none is 100% effective³, which is why its effect is judged over several months.

Tracking your hair with photos

Temporary shedding and early pattern hair loss differ mainly in how they change over time. One settles within a few months, the other moves slowly. The mirror won’t help you see the difference: the light changes, the angle changes, and you end up seeing hair loss everywhere.

Comparable photos will. Take the same photo every week: same room, same light, hair dry and styled the same way. Aim at the part, the crown and the temples, where female pattern hair loss shows first.

That’s what Calvap does. Your photos stay on your phone and line up on a timeline, area by area, with a journal to note stopping the pill, a stressful stretch or a treatment. You see the trend. And when you see a doctor, you bring dated photos instead of a feeling.