Causes of hair loss

The cause of this form of hair loss is an inherited sensitivity to the male sex hormone testosterone. This sensitivity shortens the hair growth phase and the hair follicles shrink. The shrinking follicles initially produce only short and thin hairs (vellus hairs).

These can remain or fall out. New hairs can then no longer be formed. Because of the sensitivity to the male sex hormone, men are particularly affected by this form of hair loss.

Although women also produce small amounts of testosterone, they suffer this form of hair loss much less frequently. During the menopause, which is accompanied by strong hormonal changes, the risk of hair loss in women is significantly increased. In this form of hair loss, the hair thinning starts at the temples and forehead.

This results in receding hairline and a bald forehead. Then the hair thins out at the back of the head, resulting in a toning effect. In young adult men, slow hair loss often begins between the ages of 20 and 25.

To date, the exact causes of this form of hair loss have not been explained in detail.It is believed that hair loss is caused by disorders of the immune system. This would mean that the body’s own defense cells (immune cells), erroneously attack the hair roots. These are responsible for hair growth.

Through the defense cells, the hair production is stopped and the hair falls out. It is assumed that the hair roots are not completely destroyed, but only inactivated. So it is possible that they suddenly become active again and produce new hair.

The fact that many affected persons have other autoimmune diseases, such as neurodermatitis or hay fever, supports this thesis. A genetic predisposition as a cause is also being discussed, as circular hair loss occurs more frequently in families in about 20% of patients. In this form of hair loss, coin-sized, round to oval bald spots are found in various places.

In their marginal zone, so-called exclamation mark hairs become visible when viewed under magnification. These are thin, short, broken off hairs, which become thinner towards the scalp. The bald spots are preferably visible at the back of the head or on the sides, but can also occur on the entire head.

In addition, the hair can also fall out completely in this form of hair loss. In many cases, the hair grows back after a few months. However, relapses can occur.

Hormonal and hereditary hair loss (Alopecia androgenetica)
Circular hair loss (Alopecia areata)

In general, diffuse hair loss damages the hair roots, causing diffuse hair loss. The damage to the hair roots can have various causes. These include, for example, taking medication as part of chemotherapy (cystostatic drugs).

But also infectious diseases such as scarlet fever or typhoid fever, thyroid dysfunction, prolonged malnutrition or hormonal changes during pregnancy, by taking hormone-containing medication (e.g. “pill”) or during menopause can lead to diffuse hair loss. Likewise, an inflammatory disease of the scalp (e.g. psoriasis of the scalp) or a lot of stress can trigger hair loss. In many cases, it is a natural sign of old age.

The diffuse hair loss does not cause any bald visible areas, but the entire hair thins out. If a cause for the hair loss is found and treated, the hair usually grows back again and the hair loss disappears. A fungal infection of the scalp (tinea capitis) can lead to hair loss in infected areas.

This usually affects children. Through prolonged pressure or rubbing of the scalp, it can be damaged and lead to hair loss in the affected areas. Likewise, strong pulling of the hair (traction alopecia) can lead to hair loss.

The hair roots are damaged by the strong tension. Also by a mental illness, which leads to compulsive hair pulling out, cutting or pulling at the hair, the hair thins. Those affected often feel a feeling of pressure relief for a short time.

A congenital disposition disorder of the hair (anagen hair) leads to thin, brittle hair and is already noticeable in early childhood. The hair structure is changed by an inherited defect. Another cause of hair loss can be a zinc deficiency.

Diffuse hair loss (Alopecia diffusa)
Other causes of hair loss

The connection between physical stress and hair loss has long been considered proven. Physical stress can be, for example, pregnancy, surgery or high fever. Stress causes a certain number of hair follicles (not all!)

to move from the growth phase to the rejection phase, which lasts 2-4 months. After this time, the hairs of the affected follicles fall out simultaneously. The hair loss is distributed over the whole head and only leads to thinning (diffuse hair loss), because unaffected follicles continue to have normal hair growth.

After the loss, the affected hair follicles grow normal hair again. A connection between psychologically caused (psychogenic) stress and hair loss has long been considered a myth. However, today it can be considered proven that there are interactions.

Only in the case of male hormone-induced hair loss (Alopecia androgenetica) does stress seem to have no influence. Acute or chronic psychogenic stress can cause diffuse hair loss by a mechanism similar to physical stress. However, this is usually an exclusion diagnosis after checking all physical causes.It should also be noted that psychogenic stress can in turn cause physical changes (physical stress), for example when weight is lost in a state of mourning.

These changes can also lead to hair loss. Furthermore, psychogenic stress can aggravate hair loss caused by other factors. These include circular hair loss (alopecia areata), in which hair falls out in waves in sharply defined, round areas.

This is caused by an inflammation at the hair roots mediated by nerve fibers: each hair root is reached by a network of nerve fibers, which emit various transmitters, through which they are in contact with inflammatory cells. Psychological stress increases the number of nerve fibers and this causes activation of inflammatory cells, tissue inflammation and cell death of hair follicle cells. As a result, hair growth is stopped and hair loss occurs.

Overall, it is also important to consider the reverse relationship. Hair loss usually triggers psychological stress, which in turn can aggravate the hair loss. If one suffers from stress and hair loss, physical causes should nevertheless be ruled out by a doctor first.

In addition, the sources of stress should be eliminated. Sufficient sleep, relaxation techniques and time management in the sense of more space for leisure time help. In case of mental illness or very serious mental crises, psychotherapy should be used. In all cases it helps more to fight stress as a trigger or cofactor of hair loss than to treat hair loss itself as a symptom.