What actually causes hair loss

Hair loss has more than one cause, and the treatment that works depends entirely on which one you are dealing with. Some causes are permanent if left alone but respond well to medication. Others fix themselves once the underlying trigger is sorted out. Getting the diagnosis right is the whole game, so it helps to know what the main causes look like before you decide what to do about yours.

Below are the causes an HPCSA-registered doctor sees most often, roughly in order of how common they are in South African patients.

Androgenetic alopecia (male and female pattern hair loss)

This is by far the most common cause, and it accounts for the large majority of long-term hair loss in both men and women. It is genetic, and it is driven by a hormone called DHT (dihydrotestosterone). If you have inherited follicles that are sensitive to DHT, that hormone gradually shrinks them over years. Each new hair grows a little finer and a little shorter than the last, until the follicle produces almost nothing you can see.

In men it usually shows up as a receding hairline and thinning at the crown. In women it is more often a general thinning across the top of the scalp with a widening part line, while the frontal hairline tends to stay put. It is slow, it is progressive, and it does not reverse on its own. The good news is that it is also the type most treatments are built for.

How it is treated

The evidence-based options are oral finasteride for men, which is a 5-alpha-reductase inhibitor that lowers DHT, and topical minoxidil for men and women, which improves blood flow to the follicle and prolongs the growth phase. For some women a doctor may consider spironolactone, a prescription medicine used off-label. Finasteride is not suitable for women who are or may become pregnant. Any of these is a decision to make with a registered doctor, not off the shelf. There is more detail on finasteride versus minoxidil if you want to compare them.

Telogen effluvium (stress and shock shedding)

This is the sudden, alarming kind. You notice far more hair than usual coming out in the shower or on the pillow, often handfuls at a time, and it can seem to happen everywhere on the scalp at once. What has happened is that a physical or emotional shock has pushed a large batch of follicles into their resting phase early, and a few months later they all shed together.

Common triggers include:

• A high fever, serious infection or illness (including after Covid)
• Major surgery or a general anaesthetic
• Childbirth (post-partum shedding is very common and usually settles)
• A crash diet or rapid weight loss
• Severe emotional stress, grief or burnout
• Starting or stopping certain medicines, including the contraceptive pill

The catch is timing. The shedding usually starts two to three months after the trigger, so by the time it appears you may have forgotten what set it off. The reassuring part is that telogen effluvium is almost always temporary. Once the trigger is behind you, the follicles are still healthy and the hair grows back over several months. It does not need finasteride or minoxidil, though a doctor may still check for iron and thyroid problems alongside it.

Nutritional and iron deficiency

Your follicles are among the most metabolically active tissue in the body, so they feel a shortfall quickly. Low iron is the big one, especially in women who menstruate, and it does not always mean full anaemia. A low ferritin (your iron store) on its own can drive thinning. Other deficiencies that matter are protein, vitamin D and, less often, zinc.

This is worth mentioning to a doctor because it is cheap to test with a blood panel and straightforward to correct. Do not start taking high-dose supplements blindly, though. Too much of some nutrients (biotin and vitamin A in particular) can cause problems of their own, and unnecessary supplements just waste money. A test first, then targeted correction, is the sensible order.

Thyroid problems

Both an underactive and an overactive thyroid can thin the hair. Because thyroid disease often comes with other clues (weight changes, tiredness, feeling cold or hot, mood changes, changes to your periods), it is a common thing to check when someone presents with diffuse shedding and no obvious trigger. A simple TSH blood test usually flags it, and treating the thyroid tends to settle the hair over time.

Medication

A number of everyday medicines list hair loss as a side effect. These include some blood thinners, beta-blockers and other blood-pressure drugs, certain antidepressants, retinoids for acne, some anticonvulsants, and of course chemotherapy. If your shedding started within a few months of a new prescription, mention it to the doctor who prescribed it. Never stop a prescribed medicine on your own to test the theory, since the condition it treats usually matters more than the hair. There is often an alternative.

Traction alopecia

This one is caused by how the hair is worn rather than by anything internal. Tight braids, cornrows, weaves, extensions, tight buns and prolonged tension on the same spot pull on the follicles day after day. Over time that constant tugging damages them. It typically shows up as thinning or a receding line at the hairline, temples and edges, exactly where the pull is greatest.

Caught early, it is reversible: loosening the styles and giving the roots a rest lets the hair recover. Left for years, the damage can become permanent, because scarred follicles do not grow back. If your edges are thinning and you wear tight protective styles often, this is the first thing to rule out.

Alopecia areata

Alopecia areata is an autoimmune condition, meaning the immune system mistakenly attacks the hair follicles. It usually appears as one or more sudden, smooth, coin-sized bald patches rather than general thinning, and it can affect the scalp, beard or elsewhere. It is less common than the causes above, it is not caused by stress alone, and it behaves unpredictably: hair can regrow on its own or the patches can spread. Because it is a distinct medical condition with its own management, it needs assessment by a doctor rather than over-the-counter hair products.

When to see a doctor

Some shedding is normal. We lose around a hundred hairs a day, and a bit more during a seasonal change or a stressful patch is nothing to worry about. It is worth getting checked, though, if you notice any of the following:

• Sudden, heavy shedding that came on over weeks
• Bald patches, or hair coming out in clumps
• Thinning together with tiredness, weight changes or other symptoms of being unwell
• A widening part or a hairline that keeps creeping back
• Redness, scaling, itching or pain on the scalp
• Hair loss in a child

Diagnosing the cause is not something to guess at from photos online, because the treatment is completely different depending on which cause you have. Pattern hair loss needs ongoing medication, a nutritional deficiency needs correcting, telogen effluvium needs patience, and traction needs a change of habit. An online consultation with an HPCSA-registered doctor can sort out which one you are dealing with and what, if anything, is worth doing.

You can read how the process works on our how it works page, and there are more short answers on the FAQ. Treatments for pattern hair loss take three to six months to show and are maintenance-dependent, so gains reverse if you stop. That is one more reason to start with a diagnosis rather than a product.

Start a hair-loss consultation

Prefer a female-focused path? Head to our page for women.

This page is general information and does not replace personal medical advice. Any diagnosis or treatment should be decided with a registered doctor who can assess your individual situation.