Why hair falls, and what it usually means

Losing 50 to 100 hairs a day is expected. If you wash twice a week, you will find several days of that at once, and washday volume is the single most common reason people believe they are losing hair when they are not.

Useful check: has your ponytail circumference actually changed? Has your parting widened over months? If both are unchanged and you simply notice hair in the drain, you are probably watching a normal process closely for the first time.

The most common cause of sudden, diffuse, alarming shedding. Something pushes an unusually large number of follicles into the resting phase at once, and roughly two to three months later they all shed together.

Typical triggers: a high fever or significant illness, surgery, childbirth, rapid weight loss, severe emotional stress, or starting or stopping certain medications.

Two things worth knowing. The delay means the trigger is usually months behind you and easy to miss, so look back rather than around. And it is generally self-limiting, recovering over six to nine months once the cause has resolved. It is frightening and usually temporary.

Sustained pulling on hair damages follicles. Tight ponytails, tight braids, heavy extensions and the same severe parting for years all apply steady tension, usually at the hairline and temples.

Early on it is entirely reversible. Left long enough it is not, because the follicle scars and stops producing. This is the cause most worth acting on immediately, because the window to fix it closes.

Signs: a receding or thinning hairline, small broken hairs at the front, soreness or tiny bumps after styling, and thinning that maps onto exactly where you pull.

Androgenetic alopecia, the most common cause of long-term thinning in both men and women. It is gradual, genetically influenced, and follows recognisable patterns: temples and crown in men, diffuse thinning with a widening parting in women.

It involves follicle miniaturisation, where follicles progressively produce finer, shorter strands until they stop. It is not caused by shampoo, oiling, hats, or washing frequency.

There are evidence-based medical treatments, and they work considerably better early, when there are still functioning follicles to preserve. This is the category where seeing a dermatologist sooner rather than later genuinely changes the outcome, and where no cosmetic product is a substitute.

• Iron deficiency, particularly low ferritin. Common, easily tested, and treatable.
• Thyroid disorders, both under and overactive, which commonly affect hair.
• Polycystic ovary syndrome and other hormonal conditions.
• Some medications, including certain blood pressure, antidepressant and acne treatments.
• Scalp conditions such as severe seborrhoeic dermatitis or psoriasis, where inflammation affects the follicle.
• Autoimmune conditions such as alopecia areata, which produces distinct round patches rather than diffuse thinning.

• Loss in defined patches, or a smooth round bald area.
• A visibly widening parting, or scalp becoming more visible over months.
• Shedding that continues heavily beyond three or four months.
• Any scalp pain, burning, scaling or scarring alongside the loss.
• Hair loss with fatigue, weight change, irregular periods or other symptoms.
• A family history of pattern loss and early signs of the same pattern.

Scarring types of hair loss are permanent once the follicle is gone, which is the strongest argument against waiting to see whether it resolves. A cosmetic routine can sit alongside medical treatment; it cannot replace it.