Shedding: why more hair falls out when treatment starts

The most common reason people abandon an effective treatment before it has had a chance to work.

Anyone starting treatment for hereditary hair loss expects less hair in the brush, not more. Yet in the first few weeks the opposite often happens. The phenomenon is called shedding, and it is the single most common reason users stop a therapy before it could work at all.

The process is fully explained by the hair cycle. And it is, paradoxically, a sign that something biological is happening.

The hair cycle in three phases

Every individual hair follows its own rhythm, independent of its neighbours.

In the anagen phase the hair grows actively. On a healthy scalp this lasts several years, which is why scalp hair can grow long while body hair cannot. Then comes the short catagen phase, a transition of a few weeks in which growth stops. After that the telogen phase begins: the hair rests in the follicle for about three to four months without growing. At the end it sheds, and a new hair begins to grow from the same follicle.

At any moment different hairs are in different phases. That is why people lose hair continuously rather than going bald periodically.

What happens during shedding

Drugs that intervene in the control of the hair cycle shorten the resting phase and trigger the transition into a new growth phase. A follicle still holding an old telogen hair has to push it out before the new hair can grow through.

The result: many hairs that were at the end of their resting phase anyway are pushed out at the same time rather than spread over weeks. The loss is compressed in time, and therefore visible.

Timing

According to dermatological reference sources, shedding on topical minoxidil generally begins between the second and sixth week of treatment and lasts around two to four weeks. Most people notice a temporary increase in hair turnover without any visible thinning resulting from it.

One important distinction that many guides omit: initial shedding is not established in the literature for finasteride. Users report it virtually never, whereas it occurs frequently with minoxidil solutions. The plausible explanation lies in the mechanism: minoxidil intervenes directly in cycle control, while finasteride acts primarily on follicle morphology.

So anyone noticing heavy hair loss on a 5-alpha-reductase inhibitor should not simply write it off as shedding, but have it assessed.

When it is not shedding

Shedding is time-limited and self-limiting. Persistent or increasing loss has other causes and should be investigated. Common differential diagnoses include:

• Telogen effluvium, a diffuse loss triggered by stress, infection, surgery, weight loss or medication. It typically sets in two to three months after the triggering event.
• Iron deficiency or thyroid dysfunction, both detectable through blood tests and treatable.
• Alopecia areata, which shows sharply defined bald patches and is an entirely different condition.
• Scarring alopecias, in which follicular tissue is destroyed. Early diagnosis is critical here, because this loss genuinely is irreversible.

A rule of thumb: if increased shedding lasts longer than about two months, have it assessed.

What helps during this phase

The hardest requirement is also the most important: keep going. Stopping during the shedding phase means the new growth phase that has been triggered is never completed. Treatment is halted at precisely the moment it begins to work.

Subjective impressions are notoriously unreliable in this phase. Judging at eight weeks is judging too early.

Frequently asked questions

This article is for general information and does not replace medical advice or diagnosis. Decisions about medication and individual treatment are made only in a personal consultation with a doctor.