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Why do hair fall out? The most common causes
Losing between 50 and 100 hairs a day is completely normal: it's part of the renewal cycle. The problem arises when renewal doesn't work and the amount lost exceeds what grows back. The causes are many, but some recur much more often than others.
Genetic and hormonal factors
The number one cause? Genetic predisposition. We're talking about androgenetic alopecia, commonly called male or female pattern baldness. It affects about 70% of men over 70 and 40% of menopausal women. The culprit is a hormone, dihydrotestosterone (DHT), which shortens the hair's growth phase. In women, the problem is often linked to hormonal imbalances: postpartum, polycystic ovary syndrome (PCOS, affecting 5-10% of women of childbearing age), or menopause.
Stress: an underestimated factor
Hormonal causes and imbalances: thyroid, pregnancy, menopause
Hormones control the hair life cycle. When something becomes unbalanced, the follicle feels it immediately. The thyroid, for example, is a hot spot: both hyperthyroidism and hypothyroidism can trigger hair loss causes hormonal. With hyperthyroidism, hair becomes fine and brittle. With hypothyroidism, it dries out and falls out in clumps. A blood test (TSH, FT3, FT4) is usually enough to determine if the thyroid is involved.
Then there's pregnancy. During the nine months, estrogen levels keep hair in the anagen phase longer than normal. The mane seems thicker, it's true. But after childbirth, the hormonal crash pushes many follicles into the telogen phase simultaneously. This happens to about 40-50% of women, and the peak of loss occurs between 2 and 4 months after delivery. Don't panic: it usually resolves on its own in 6-12 months, but sometimes nutritional support is needed.
Menopause changes the game. Estrogen levels drop, while androgens remain more or less the same. The ratio shifts and the follicle responds by producing thinner and shorter hair, especially on the top of the head. It's a progressive thinning, not patchy loss. It affects about 60% of postmenopausal women, although many don't notice it immediately. Diagnosis is made with trichoscopy and hormonal history.
Another common imbalance is polycystic ovary syndrome (PCOS), which raises androgens and can accelerate frontal and parietal thinning. Not all women with PCOS lose hair, but when it happens, it's quite characteristic. Hormone replacement therapy or birth control pills can also influence the hair cycle, sometimes for the better, sometimes for the worse, depending on the progestin used.
The good news? Once the hormonal cause is identified, intervention is possible. Thyroid therapy (levothyroxine or antithyroid drugs), for example, often makes hair regrow within a few months. After pregnancy, patience is the first medicine. In menopause, topical treatments like minoxidil or antiandrogen therapies (finasteride under medical supervision, or spironolactone) can yield good results. But don't improvise: you need an endocrinologist or trichologist to interpret the tests and choose the right path.
Diseases that cause hair loss
Not all hair loss is due to stress or genetics. Certain diseases trigger the problem as a direct side effect. And it's important to recognize them, because treating the underlying cause often stops the loss.
The thyroid is among the top suspects. Both hypothyroidism and hyperthyroidism alter the follicle cycle. When the thyroid doesn't function properly, the hair stays in the resting phase instead of regrowing. The result? Diffuse loss, not patchy. Often the first sign is increased shedding 2-3 months after the hormonal imbalance.
Then there's alopecia areata. It's an autoimmune disease: the immune system attacks the follicles. The loss is rapid and in round patches. It can occur at any age. In some cases, it stops on its own; in others, it progresses to involve the entire scalp.
Lichen planopilaris: when inflammation destroys the follicle
Less known, but insidious. Lichen planopilaris is a chronic inflammatory disease that affects the scalp. The cause is autoimmune: lymphocytes attack the upper part of the follicle. The result? Scarring and permanent loss. Recognizing it early is crucial. Initial signs are itching, burning, and localized redness. Then shiny patches without pores appear. Once the follicle is replaced by scar tissue, nothing grows back. Lichen planopilaris accounts for a significant share of the cicatricial alopecia cases diagnosed each year. Treatment involves topical or intralesional corticosteroids, but diagnosis often comes late, when the damage is already done.
Systemic lupus erythematosus: hair loss as a warning sign
Lupus is another autoimmune disease that can cause hair loss. It doesn't only affect the scalp: it involves skin, joints, and internal organs. But hair loss is often one of the first symptoms the patient notices. It can be diffuse or patchy, with thinning areas and fragility. In some cases, the loss is reversible if the underlying disease is controlled. Immunosuppressive drugs, such as hydroxychloroquine, help reduce systemic inflammation. It is not unusual for lupus to be identified precisely because hair has been falling out in clumps for months.
Nutritional deficiencies: which vitamins and minerals are essential?
The connection between diet and hair loss causes is closer than many think. When the body doesn't get enough specific vitamins and minerals, hair production slows or stops. A nutritional deficiency is among the first factors to rule out in someone presenting with diffuse thinning.
Iron: the most often overlooked mineral
The data is clear: iron deficiency is one of the most frequent causes of hair loss in women of childbearing age. About 30% of women between 20 and 49 have low iron stores, even without overt anemia. Hair enters the resting phase (telogen) and falls out more than normal. If heavy menstruation or a diet low in red meat, legumes, and leafy green vegetables is added, the problem amplifies. A simple ferritin test (optimal value above 70 ng/mL) clarifies the situation immediately.
Zinc, vitamin D, and biotin: the other key players
Zinc participates in keratin synthesis. A deficiency manifests with brittle hair and thinning areas, sometimes resembling alopecia areata. Vitamin D, on the other hand, regulates the hair follicle cycle: blood levels below 20 ng/mL are associated with a higher incidence of telogen effluvium. As for biotin (vitamin B7), deficiency is rare in those who eat eggs and nuts, but can occur in restrictive diets or after prolonged antibiotic use.
Other nutrients to keep an eye on:
- Vitamin B12 - essential for cell division of the hair bulb. Deficient in vegans and those with atrophic gastritis.
- Vitamin C - indispensable for iron absorption.
- Selenium and copper - enzymatic cofactors for hair pigmentation and structure.
Before buying supplements, it's better to test actual levels with a blood test. An excess of zinc, for example, blocks copper absorption and worsens the situation.
When to worry? Warning signs and diagnosis
Not all hair that ends up on the brush is a problem. A daily loss of 50-80 hairs is normal, part of physiological turnover. The alarm bell rings when the count exceeds 100-120 and remains above for weeks. Or when hair visibly thins, the scalp becomes more exposed, the part widens.
There are signs that should not be ignored. If you find whole clumps on the pillow in the morning, or when running your hands through your hair, five to ten remain attached, it's time to act. The same if you notice smooth, completely hairless areas, which may indicate alopecia areata. Another indicator? Constant itching, stubborn dandruff, redness, or localized pain - nothing normal, often there is underlying inflammation.
The diagnostic pathway
The first step is simple: schedule a visit with a dermatologist or trichologist. In Italy, it can be found both in the public system (with varying wait times) and in private practice, where an initial consultation costs between 80 and 150 euros. No self-diagnosis on Google: what seems like "stress" to you could be an iron deficiency or thyroid dysfunction.
The trichologist begins with a visual exam, then performs the pull test - gently pulls a strand to see how many hairs come out. If more than 3-5 per pull come out, something is off. This is often followed by trichoscopy, a magnifying lens that allows viewing the scalp and follicles under a microscope. Not painful, lasts ten to fifteen minutes.
For a more precise diagnosis, a trichogram can be used, a microscopic analysis of 50-100 plucked hairs (unpleasant but effective) to understand which phase of the life cycle they are in. Those in the anagen (growth) phase should be 70-80% of the total. If they fall below 60%, the cycle is shortening.
Blood tests complete the picture. The doctor prescribes a test with a complete blood count, ferritin levels (below 30 ng/ml is a problem), vitamin D, thyroid hormones (TSH, FT3, FT4), and often a complete hormonal profile in women to rule out polycystic ovary syndrome. In men, DHT is evaluated.