Why Is My Hair Falling Out? 10 Causes a Trichologist Checks First

Quick answer: Hair falls out for lots of reasons, and most of them are fixable. The common ones are a shock to the body three months earlier (illness, stress, surgery, a baby, a crash diet), low iron, thyroid problems, hormonal changes, pattern hair loss that runs in families, tight hairstyles, scalp conditions, medicines, and sometimes an immune condition called alopecia areata. The pattern of the loss, and the timing, usually tell you which one it is.

"Why is my hair falling out?" is the question I hear most at Tess Hair and Scalp Clinic in Belfast. It's usually asked with a slightly panicked hand gesture towards the plughole.

So let me do what I do in clinic: slow down, look at the pattern, look at the timing, and go through the usual suspects one by one. By the end you should have a good idea which of these is yours, and what to do about it.

One thing first. According to the NHS, we all lose between 50 and 100 hairs a day without noticing. So the question isn't "am I losing hair?" (you are, so am I). It's "am I losing more than I'm growing back, and why?"

First, work out the pattern

Before the causes, two quick questions that narrow things down a lot.

Is it everywhere, or in one place? Shedding from all over the head (you notice it in the shower, on the pillow, in the brush) points to a whole-body cause: stress, illness, iron, thyroid, hormones. Thinning in one area (the crown, the temples, the parting, a round patch) points to pattern hair loss, traction from hairstyles, or alopecia areata.

Did something happen about three months ago? Hair has a delay built in. A shock to the body pushes hairs into their resting phase, and they fall out roughly three months later. So if you're shedding now, think back to the summer, not last week.

Now the list.

1. A shock to the body three months ago (telogen effluvium)

This is the most common cause of sudden, all-over shedding I see. The medical name is telogen effluvium, and the British Association of Dermatologists explains it well: an illness, a high fever, surgery, childbirth, a very stressful event, crash dieting or starting a new medicine disrupts the hair cycle. About three months later, far more hairs than usual fall out at once.

The good news: it usually stops on its own within three to six months and the hair grows back. The less good news: it takes many months for the volume to come back, and it can return if the trigger (low iron, say) isn't dealt with.

Tell-tale sign: handfuls of hair all over, starting suddenly, with a thinner ponytail but no bald patches.

2. Low iron

Iron deficiency is one of the temporary causes the NHS lists, and in my experience it's the one most often missed, especially in women with heavy periods, people who've recently been pregnant, and anyone eating little or no red meat.

The NHS page on iron deficiency anaemia lists hair loss among its symptoms, alongside tiredness, breathlessness and pale skin. A simple blood test from your GP will tell you. Please don't just start taking iron tablets on a hunch: too much iron isn't good for you either, and you want to know your starting point.

Tell-tale sign: all-over shedding plus tiredness, feeling the cold, or heavy periods.

3. Thyroid problems

Your thyroid gland sets the pace for a lot of your body, including how fast hair grows. Both an underactive and an overactive thyroid can cause diffuse thinning. It often comes with other clues: weight changes, feeling tired or wired, dry skin, feeling too hot or too cold.

Again, this is a blood test at your GP. If your thyroid is the cause, hair usually recovers once treatment settles, though it can take months.

Tell-tale sign: all-over thinning with tiredness, weight change or temperature changes.

4. Pattern hair loss (it runs in families)

The NHS calls this male and female pattern baldness, and it's the most common type of permanent hair loss. In men it shows as a receding hairline and a thinning crown. In women it usually shows as a widening parting and a thinner ponytail, with the hairline mostly kept.

It's driven by genes and hormones, and it's gradual rather than sudden. There are proven treatments (minoxidil for men and women, and prescription options for men through a doctor), but they work best started early, and they only work while you keep using them.

Tell-tale sign: slow thinning in a specific pattern, often with a parent or grandparent who had the same.

5. Hormonal changes

Pregnancy, the months after birth, stopping or starting the contraceptive pill, perimenopause and menopause, and conditions like PCOS all shift your hormones, and your hair notices.

Shedding after a baby is so common it has its own name (postpartum hair loss) and usually settles within a year. Menopause-related thinning tends to be gradual and can overlap with pattern hair loss. If hormones are the likely cause, your GP is the right first stop, and a trichologist can help with the hair side while that's being looked at.

Tell-tale sign: shedding that lines up with a pregnancy, a change in contraception, or menopause symptoms.

6. Stress

Yes, stress really can make your hair fall out, but not the way people imagine. It doesn't happen overnight, and it isn't the stress itself, it's the shock to your system pushing hair into the resting phase, so it shows up around three months later (see cause number one).

A bad few months, a bereavement, a house move, exam season, a divorce: I've seen all of these turn up in the hair about a season later.

Tell-tale sign: all-over shedding, three months after a genuinely rough patch.

7. Tight hairstyles and extensions (traction alopecia)

This one is mechanical rather than medical. Tight braids, high ponytails, buns, weaves and heavy extensions pull constantly on the hair root. Over time, the follicle gives up. It usually shows first at the hairline and temples, the "edges".

Caught early, it recovers when you loosen things up. Left for years, it can become permanent. We fit extensions and braids here, and we also treat the damage, so you'll get a straight answer from us on whether your style is costing you hair.

Tell-tale sign: thinning at the edges or wherever the pull is, with small bumps or soreness along the hairline.

8. Scalp conditions

A scalp that's inflamed, flaky, greasy or itchy isn't a good place to grow hair. Seborrhoeic dermatitis (heavy, greasy dandruff), scalp psoriasis, fungal infections and product build-up can all increase shedding or stop hair growing well.

The clue is that the scalp itself has symptoms: flakes, redness, itch, spots or a waxy feel. Sort the scalp and the hair usually follows. If you've already tried the unclogging your follicles advice and it hasn't shifted, it's time for a proper look.

Tell-tale sign: shedding plus an itchy, flaky, greasy or sore scalp.

9. Medicines

Some medicines list hair thinning as a side effect. The NHS mentions cancer treatment, and others can include some blood pressure tablets, blood thinners, some antidepressants, acne medicines, and hormone treatments. Starting a new medicine is also one of the triggers the British Association of Dermatologists lists for telogen effluvium.

Never stop a medicine because of your hair without talking to your GP or pharmacist. Often there's an alternative, or the shedding settles.

Tell-tale sign: shedding that started two to three months after a new prescription.

10. Alopecia areata

This is an immune condition where the body attacks its own hair follicles, causing smooth, round bald patches to appear, sometimes quite suddenly. It can affect anyone at any age. In many cases the hair grows back on its own, and there are treatments for when it doesn't.

If you've found a smooth patch rather than general thinning, see your GP. A trichologist can support you alongside that.

Tell-tale sign: one or more smooth, round, completely bald patches, often noticed by a hairdresser.

What about breakage?

Sometimes "my hair is falling out" is actually "my hair is snapping off". If the hairs you find are short, with no little white bulb on the end, and your hair feels rough or frizzy, you may be dealing with breakage from heat, bleach or rough handling rather than hair loss. We wrote about the difference between breakage and shedding separately, and it changes what you should do next.

Common mistakes I see

• Starting three products at once. If something works, you won't know which. If something irritates you, same problem.

• Washing less to "save" hair. Washing doesn't cause hair loss. The hairs in the plughole were already loose. Washing less just saves them up and gives you a scarier shower.

• Buying supplements before a blood test. If you're not low in something, more of it won't help, and some (like iron) can do harm in excess.

• Waiting a year to get it looked at. Pattern hair loss and traction alopecia are both much easier to treat early.

When to see your GP, and when to see a trichologist

See your GP if you have bald patches, a sore or very inflamed scalp, hair loss alongside other symptoms (tiredness, weight change, heavy periods), or if it's affecting your wellbeing. The NHS suggests seeing a GP first to find the cause, and I agree. Ask about blood tests for iron, thyroid and vitamin D.

See a trichologist for a close look at your scalp and hair, to work out which type of hair loss you have, and for a practical plan: what to wash with, how to style, which treatments suit you, and when you need a doctor. If you're not sure which you need, our post on whether to see a trichologist walks through the signs.

Frequently asked questions

Why is my hair falling out all of a sudden?

Sudden all-over shedding is usually telogen effluvium: a shock to the body about three months ago, such as illness, surgery, childbirth, a crash diet, stress or a new medicine. It usually stops on its own, but get low iron and thyroid checked.

Why is my hair falling out in clumps?

Clumps in the shower are usually heavy shedding, not patches. If you can see smooth, bald, round patches on the scalp, that may be alopecia areata and is worth a GP visit.

Can stress cause hair loss?

Yes, but with a delay. Stress pushes hair into a resting phase and the shedding shows up around three months later. It usually recovers once things settle.

Which blood tests should I ask for?

A full blood count, ferritin (iron stores), thyroid function and vitamin D are the usual starting points. Your GP will decide what's right for you.

Will my hair grow back?

If the cause is temporary (illness, stress, iron, hormones, medicines) it usually does, over several months. Pattern hair loss and long-standing traction alopecia need treatment rather than waiting.

Not sure which one is you?

Book a hair and scalp analysis with Theresa at Tess Hair and Scalp Clinic, 77a Botanic Avenue, Belfast, or call 028 9096 4731. We look at your scalp up close, go through your history, and tell you plainly what's going on and what to do next. You can see our treatments and prices here.

About the author: Theresa Anthony is the trichologist at Tess Hair and Scalp Clinic, 77a Botanic Avenue, Belfast BT7 1JL, where hair loss treatment and a full hair salon sit under one roof.

Sources: NHS: Hair loss · British Association of Dermatologists: Telogen effluvium · NHS: Iron deficiency anaemia