Why Is My Hair Suddenly Falling Out? The Most Common Causes of Excessive Shedding

If your hair suddenly seems to be everywhere, in the shower, on your brush, on your clothes and around the house, one common explanation is telogen effluvium. This is a type of excessive hair shedding that can happen a few months after something has disrupted the normal hair-growth cycle, such as illness, major stress, childbirth, significant weight loss or iron deficiency.

Sudden hair loss has other possible causes too, so the timing and pattern matter. Diffuse shedding from all over the scalp is different from developing distinct bald patches, a gradually widening parting or hair loss alongside an inflamed scalp. If the change is new, significant or worrying you, a GP can help work out what may be causing it.

The short answer

Hair does not usually start shedding heavily for no reason, but the trigger may not be obvious by the time you notice it.

The British Association of Dermatologists explains that telogen effluvium often begins around three months after a trigger. Possible triggers include childbirth, serious illness, major surgery, significant weight loss, extreme dieting, severe stress, scalp problems, new medicines and stopping hormonal treatment.

The NHS also lists illness, stress, cancer treatment, weight loss and iron deficiency among causes of temporary hair loss.

Sometimes no trigger can be identified. The British Association of Dermatologists notes that no cause is found in around one in three people diagnosed with telogen effluvium.

So if you are asking “Why is my hair falling out now?”, it is worth thinking back over the previous several months rather than only the past week.

What counts as excessive hair shedding?

Everyone loses hair as part of the normal hair cycle.

The British Association of Dermatologists states that it is normal to lose around 30 to 150 hairs from the scalp each day. You probably do not notice most of them individually.

With telogen effluvium, more hairs than usual move into the resting phase of the cycle and are eventually shed. This can make normal activities suddenly look alarming.

You may notice:

much more hair in the shower
a larger amount in your brush or comb
hairs coming away when you run your fingers through your hair
more loose hairs on clothing, bedding or floors
a ponytail that feels less full
a general reduction in volume across the scalp

Counting every hair is rarely helpful. The change from what is normal for you is usually more meaningful.

Why can shedding start months after the trigger?

Hair follicles work on a delayed timetable.

Each follicle moves through stages of active growth, transition, rest and shedding. A trigger can push a larger than usual number of hairs from the growing stage towards the resting stage.

Those hairs do not necessarily fall immediately.

In telogen effluvium, the increased shedding commonly becomes noticeable around three months after the event that triggered it. This delay can make the cause easy to miss.

For example, you may have had a high fever in January, felt completely recovered by February and only notice substantial shedding in March or April.

If your hair has suddenly started falling out, think back roughly two to four months and consider whether anything significant happened during that period.

Illness and fever can trigger sudden hair loss

A significant illness can trigger temporary diffuse shedding.

The British Association of Dermatologists lists severe infection or illness among possible causes of telogen effluvium. The NHS also lists illness as a cause of temporary hair loss.

This can happen even if the illness itself did not involve your scalp.

By the time the shedding starts, you may feel completely well again. That does not necessarily mean the two events are unrelated because of the delay in the hair cycle.

If the shedding follows an illness and fits the pattern of telogen effluvium, hair growth can recover as the cycle settles. But it is still worth seeking advice if you are unsure about the cause or the loss is substantial.

Major stress can cause excessive hair shedding

Stress can affect hair, but “it is probably stress” should not be used to dismiss unexplained hair loss.

The NHS and British Association of Dermatologists both recognise significant stress as a possible trigger for temporary shedding.

This usually refers to substantial physiological or emotional stress rather than the ordinary frustration of a busy week.

A bereavement, major life event, serious period of anxiety or another sustained strain can potentially contribute to telogen effluvium.

At the same time, hair loss can have several causes. If you are experiencing significant shedding, it is reasonable to ask for other possibilities to be considered rather than assuming stress explains everything.

Childbirth can cause postpartum shedding

Increased hair shedding after pregnancy is common and can be dramatic.

During pregnancy, hormonal changes can alter the hair cycle. After birth, more hairs can enter the shedding stage around the same time.

The British Association of Dermatologists lists childbirth as a recognised trigger for telogen effluvium.

This can make hair feel much less dense, particularly around the hairline, even though the follicles have not necessarily been permanently lost.

If postpartum hair loss is worrying you, seems patchy rather than diffuse, continues for a long time or comes with other symptoms, speak to your GP. Postpartum changes do not rule out other causes such as iron deficiency or thyroid problems.

Significant weight loss and restrictive dieting can affect hair

Hair follicles respond to changes in the body’s available energy and nutrients.

The NHS lists weight loss as a possible cause of temporary hair loss, while the British Association of Dermatologists includes marked weight loss and extreme dieting among triggers for telogen effluvium.

The issue is not that there is one magical “hair food” you have stopped eating.

Substantial calorie restriction can be a physiological stressor. Depending on the diet, you may also be getting less protein, iron, zinc or other nutrients than your body needs.

If your shedding began a few months after rapid or substantial weight loss, mention this to your GP.

If eating enough or maintaining a varied diet has become difficult, support from a healthcare professional or registered dietitian can be more useful than buying multiple hair supplements.

Iron deficiency can contribute to hair loss

Iron deficiency is another recognised cause of temporary hair loss.

The NHS lists hair loss among the less common symptoms of iron deficiency anaemia. The British Association of Dermatologists also identifies iron deficiency as a possible underlying cause of telogen effluvium.

This is particularly worth discussing if you also have symptoms such as tiredness, breathlessness, palpitations or headaches, or if you have a reason to be at greater risk of iron deficiency.

Heavy periods are a common cause of iron deficiency anaemia, according to the NHS.

Do not start high-dose iron simply because your hair is shedding. A blood test can help establish whether iron deficiency is actually present, and your GP can investigate why your iron may be low.

Thyroid conditions can affect your hair

Both an underactive and overactive thyroid can affect the hair cycle.

The British Association of Dermatologists notes that thyroid conditions may be investigated when assessing telogen effluvium. The NHS also lists dry hair or hair loss among possible symptoms of an underactive thyroid.

Other symptoms can provide useful clues.

An underactive thyroid can cause tiredness, feeling cold, weight gain, constipation and difficulty concentrating, among other symptoms. An overactive thyroid can cause symptoms including anxiety, heat sensitivity, palpitations and weight loss.

These symptoms have many possible explanations, so they cannot diagnose a thyroid condition on their own.

If hair shedding is accompanied by other changes in how you feel, tell your GP. Blood tests can assess thyroid function when clinically appropriate.

Medicines and hormonal changes can trigger shedding

Some medicines can contribute to hair loss.

The British Association of Dermatologists lists new medicines among possible triggers for telogen effluvium, including some anticoagulants and medicines used to treat high blood pressure.

Stopping hormonal treatment can also be a trigger. The BAD specifically mentions discontinuing the contraceptive pill as one example.

This does not mean you should stop a prescribed medicine if you think it is affecting your hair.

Speak to your GP or pharmacist instead. They can review the timing, assess whether the medicine could be relevant and discuss appropriate options.

If you recently started, stopped or changed any medicine or hormonal treatment, include that information when discussing your hair loss.

Surgery can trigger hair shedding

Major surgery can place considerable physiological stress on the body.

The British Association of Dermatologists includes major surgery among recognised triggers for telogen effluvium.

Again, the delay matters. Hair may begin shedding weeks or months after you have recovered from the procedure, making the connection less obvious.

If you had surgery several months before your hair started falling out, mention it during your assessment.

Could it be female pattern hair loss instead?

Female pattern hair loss usually looks different from a sudden episode of shedding.

The British Association of Dermatologists describes it as gradual thinning, often over the top of the scalp, with increased visibility of the scalp and widening of the central parting. The frontal hairline is often relatively preserved.

Telogen effluvium tends to cause more noticeable shedding from across the scalp.

However, the two can happen together. The BAD notes that telogen effluvium can sometimes reveal underlying androgenetic alopecia, also known as pattern hair loss.

You might therefore experience a sudden period of shedding and later notice that your hair does not return completely to its previous density.

If thinning continues after the heavy shedding settles, a GP or dermatologist can assess whether another type of hair loss may also be present.

What if the hair loss is in patches?

Distinct bald patches are less typical of telogen effluvium.

One possible cause is alopecia areata, an autoimmune condition that can cause patches of hair loss. The British Association of Dermatologists explains that the immune system mistakenly targets hair follicles, leading to hair loss.

Other conditions can also produce patchy hair loss, so it is better not to diagnose the pattern yourself.

If you develop one or more bald patches, arrange an appointment with your GP. An examination of the scalp can often provide information that blood tests alone cannot.

Could your hairstyle be causing hair loss?

Repeated tension on the hair can cause traction alopecia.

The British Association of Dermatologists explains that tight hairstyles can pull on the hair roots over time. Styles associated with traction can include tight braids, cornrows, dreadlocks, extensions, weaves and repeatedly tight ponytails or buns.

Early traction alopecia can sometimes improve if the pulling force is removed. Long-standing traction can eventually lead to permanent hair loss in affected areas.

This tends to produce hair loss in areas under repeated tension rather than sudden diffuse shedding from the whole scalp.

There is no need to avoid any particular hairstyle completely. The useful principle is to notice persistent pulling, soreness or tension and give the hairline and scalp regular relief.

Could it actually be breakage rather than shedding?

Hair breaking and hair shedding are easy to confuse.

A shed hair has come out from the follicle. A broken hair has snapped somewhere along its shaft.

Breakage may leave lots of shorter pieces of hair and uneven lengths. It can be encouraged by repeated bleaching, chemical processing, high heat, friction, tight styling or rough handling.

True excessive shedding tends to involve full-length hairs coming away from the scalp.

You can also have both at the same time.

If your hair feels less dense but you are not seeing many full-length shed hairs, consider whether breakage may be contributing. A hairdresser can help assess damage to the lengths, while unexplained loss from the scalp is better discussed with a healthcare professional.

Can scalp conditions make hair fall out?

Yes, some scalp conditions can be associated with hair loss or breakage.

An inflamed, painful, very itchy, scaly or scarred scalp deserves professional assessment, particularly if hair is also being lost.

This is different from uncomplicated telogen effluvium. The British Association of Dermatologists notes that telogen effluvium usually does not produce other scalp symptoms, although some people report tenderness or altered sensations.

If your scalp itself looks or feels significantly different, mention that when you seek advice. Photographs can be useful if symptoms come and go.

How long does excessive shedding last?

If the cause is telogen effluvium, the outlook is often reassuring.

The British Association of Dermatologists states that the shedding phase usually lasts around three to six months. After that, new hair begins to grow.

It can take considerably longer for the overall volume to look as it did before because new hairs need time to gain length.

If the trigger continues, or if there is an untreated underlying cause such as iron deficiency, shedding may persist.

Telogen effluvium lasting longer than six months is described as chronic telogen effluvium.

The timeline is one reason not to judge a hair routine after a few days or weeks. Hair changes happen slowly.

What should you do if your hair suddenly starts falling out?

A simple approach is usually more useful than immediately buying treatments.

Look at the pattern. Is the hair shedding all over, thinning gradually in one area, breaking, or coming out in patches?
Think back several months. Consider illness, fever, surgery, major stress, childbirth, weight loss, dieting or changes to medicines and hormones.
Notice other symptoms. Fatigue, heavy periods, weight changes, feeling unusually hot or cold, scalp inflammation and other changes can all be useful information for your GP.
Keep hair care gentle. Avoid excessive pulling, harsh brushing and unnecessary tension while shedding is heavy.
Do not start several supplements at once. Hair loss is not proof that you are deficient in vitamins or minerals.
See your GP if you are concerned. They may be able to identify the cause from your history and scalp examination, with blood tests if appropriate.

You may prefer to take a photograph of your parting or hairline once a month rather than checking it every day. This can make gradual changes easier to judge without constantly focusing on individual shed hairs.

Do you need a special shampoo while your hair is shedding?

Usually not.

A shampoo cleans the scalp and hair. Changing shampoo does not correct iron deficiency, thyroid disease, postpartum hormonal changes or the delayed hair-cycle response of telogen effluvium.

You can choose whichever gentle shampoo makes your scalp and hair feel comfortable.

If your scalp is itchy, inflamed or very flaky, however, that is worth mentioning to your GP or pharmacist because you may have a scalp condition that needs a different approach.

There is also no need to wash your hair less often simply to avoid seeing shed hairs. Washing generally releases hairs that were already ready to shed.

Will the hair grow back?

That depends on the cause.

Temporary telogen effluvium commonly improves once the trigger has passed or an underlying problem has been addressed. The British Association of Dermatologists notes that medication does not speed up the regrowth process in telogen effluvium.

Female pattern hair loss behaves differently and may gradually progress without treatment. Scarring forms of alopecia can also have a different outlook.

This is why identifying the type of hair loss matters more than finding one product labelled “hair growth”.

If your shedding is temporary, seeing new shorter hairs appear over time can be a sign of regrowth. They still need months to gain enough length to contribute noticeably to overall volume.

When to get professional advice

The NHS advises seeing a GP if you are worried about hair loss.

It is particularly sensible to seek advice if:

hair loss started suddenly and you do not know why
you are shedding substantially more hair than usual
shedding continues for several months
you have distinct bald patches
your parting is becoming progressively wider
your scalp is painful, inflamed, very itchy, scaly or scarred
you have heavy periods, fatigue, breathlessness or other possible signs of iron deficiency
you have unexplained weight changes or other symptoms that could suggest a thyroid condition
hair loss began after starting or changing a medicine
you have experienced substantial or unexplained weight loss
you are concerned that your diet may not be meeting your nutritional needs
you are losing eyebrows, eyelashes or body hair as well
hair loss is affecting your wellbeing

Seek prompt medical advice if hair loss occurs alongside other symptoms that make you acutely unwell.

You do not need to work out the diagnosis before making an appointment. The pattern, timing and events in the months before the shedding began are often the most useful information you can bring.

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