The hair

Hair is an annex of the skin that covers much of our body. It is formed by the root and the stem. The root is the part that remains inside the skin and arises from the hair bulb that is in small holes in the dermis: hair follicles . The stem is the part of the hair that is visible above the skin. The hair is distributed along regular lines that are called rivers and that are located around eddies. The easiest swirl to see is the one we have at the apex of the head. The hair root is in contact with a small erector muscle that is the one that stresses the hair producing the effect that we popularly know as “goosebumps”.

The hair covers the entire body except some areas such as the palms of the hands and feet, part of the fingers, navel and genitals. There are two types of hair according to their characteristics: terminals and hairs . The terminal hairs are thicker and cover the scalp, eyebrows, beard and mustache, armpits and pubis. On the contrary, we find the hair in the rest of the skin and it is of less consistency and thickness. Hair that covers the scalp is called hair. That’s why when we talk about hair we always refer to head hair.

The hair of the scalp or hair is the most developed of our body. They are the ones that grow faster and can reach great length. The shape and characteristics of the hair is influenced by the breed. Thus the Eskimos and Asians have very thick and usually straight hair, while the black race usually has thinner and curly hair.

The hair grows between 0.3 and 0.5 mm daily. In a month the hair of the scalp can grow between 1 and 1.5 cm. Hair does not always grow the same way. There is a growth cycle with three different phases:
. Anagen phase: is when the hair develops more and lasts about 4 years in this phase. 85% of the hair is in this phase.
. Catagen phase: is a transition phase in which growth stops. It lasts about 3-4 months and 1% of the hair is in this phase in a normal person.
. Telogen phase: is a resting phase that lasts about 4-5 weeks and in which 14% of the hair is usually found.
During the telogen phase the hair detaches easily from the follicle, being the moment when the natural fall occurs. Each day an average of 40-50 hair falls, which is about 15,000 each year. The fall is more pronounced at the end of summer and in the fall.

Hormones have a fundamental role in hair loss, both in women and men. The hair follicle has receptors sensitive to the male hormones (dihydrotestosterone and testosterone) . This sensitivity of the hair follicles is different in each person and in the different areas of the head. The frontal and crown areas are usually more sensitive, while the neck and lateral follicles are less sensitive. For the same level of male hormones two people can react differently according to their level of sensitivity.
There are other hormones that can also play a role in hair growth and loss such as the growth hormone, thyroxine or prolactin .

We all lose about 50 hairs a day in a normal regeneration process, which has no consequences because they are renewed with follicles that are in the growth phase. When hair loss is excessive and does not recover we find a situation of alopecia that leaves less density or absence of hair in some area of the head.

Baldness is a alopecia that is permanently established in the scalp reducing the size and functionality of the hair follicles and eliminating hair in a non-recoverable way . The most frequent cause is the androgenetic that results in common baldness. It affects both men and women but is more frequent and earlier in man.

Due to the high psychological impact that alopecia represents in the population, over the years it has been investigated to try to obtain a treatment on Alopecia. The science that studies these pathologies is called Trichology.

In hair medicine we look for the causes that cause the problem of baldness to provide solutions adapted to each patient. Because there are more than 100 types of alopecia it is very important to have a good previous diagnosis.

. Androgenic or also known as “baldness” is the best known and most frequent. It usually originates in the range between 20 and 30 years. It is due to a dihydrotestosterone-dependent process that leads to the miniaturized follicles to the scalp.

Autoimmune Diseases , are those in which the immune system ignores parts of our body and acts against them. Some of them act on hair follicles causing hair loss, such as alopecia areata or lupus.

. Mental Illnesses . Who not at this time has stress problems. The rhythm of life, the evolution of society disconnects the body from the mind by overloading and generating problems in the organism, the scalp is no exception.

. Tricolomania . It is defined as a hair loss disorder by a disorderly and repeated urge to pull the hair.

Medications . Certain drugs act primarily on the interaction of hair follicle nutrition, or inhibit its growth, such as beta blockers, medications that are commonly used in the treatment of high blood pressure. Non-steroidal anti-inflammatory drugs or also called NSAIDs.

. Infections . Fungal diseases such as tinea capitis, pyoderma, mycobacteria, syphilis.

Hereditary Causes . Darier’s disease, sex-linked ichthyosis, dystrophic bullous epidermatosis, pigmenti incontinence, polycystic fibrous dysplasia.

The most frequent male alopecia is the androgenetic. They suffer, to a greater or lesser extent, 50% of men over 30 years of age and that percentage increases with age. It has a typical pattern in men that starts at the temples and continues in the frontal area and in the crown.

The origin of androgenetic alopecia responds to three factors: the genetic factor, hormonal levels and age .
The genetic factor has an important influence and explains why, given similar hormonal levels, some men lose more hair than others. Hair follicles have receptors that capture dihydrotestosterone and testosterone that have different sensitivity according to our genetic code.
The levels of male hormones also depend on each person and the level of the enzyme that transforms testosterone into dihydrotestosterone (5 alpha reductase). Some treatments are based on reducing or blocking the action of this enzyme.
Age enhances the two previous factors and determines that the hair is weaker and the follicles are more sensitive to degeneration.

Androgenetic alopecia has a typical evolution that progresses similarly in all men. In 1951 James Hamilton described a classification of male alopecia that included 8 evolutionary stages. In 1975 Norwood revised that classification and introduced some subclassification that detailed more the one carried out by Hamilton. It is currently the most used classification and on which the diagnosis of androgenetic alopecia in men is based.

On the Hamilton-Norwood scale, 7 levels of baldness differ:

. Type I: Initial baldness not noticeable at the frontal level.
Type II: Fronto-temporal baldness that draws the effect of the inputs.
. Type III: Frontal baldness with pronunciation of the entrances and baldness in the crown begins.
. Type IV: Baldness is extended in the crown area but there is still an area with hair between the entrances and the crown.
. Type V: narrows the region with hair between the entrances and the crown.
. Type VI: The frontal and crown baldness joins.
. Type VII: Baldness extends its extension and there is only one area with hair in the temporal area above the ears and in the occipital area of the neck.

Female alopecia has a more heterogeneous origin than in men, although its main cause is also androgenetic. In women, the percentage of involvement before the age of 45-50 is lower and, on the other hand, it is accentuated with the onset of menopause. Female androgenetic alopecia does not generate defined areas of baldness but produces areas of lower hair density, especially in the upper area of the head.

The origin of androgenetic alopecia in women is similar to that of men. When the increase in male hormone levels predominates, its onset is earlier. However, the usual thing is that it is the result of the sensitivity of the hair follicles to the hormonal factors , and in that case it debuts from menopause . When the onset of baldness coincides with menopause, it is because of the decrease in estrogens that act as protectors against androgens. The typical pattern begins in the midline from where the affected area is enlarged until it can form a crown, but usually maintains the frontal part.

Erich Ludwig described in 1977 classified the evolutionary stages of female androgenetic alopecia in 3 phases or stages. The initial stage begins in the middle line with a loss of density that progressively expands its presence, until in the more advanced stages a crown forms around the midline.
While in men, hormonal involvement ends the life of the hair follicle. In contrast to women, it weakens him causing less hair to grow and of lower quality, but does not generate a baldness zone until the most advanced stages.

It is a type of alopecia that occurs in women after motherhood, the result of the hormonal changes of pregnancy in which estrogen and progesterone are kept at very high levels. Therefore, most women experience at this stage an improvement in hair density and growth. After childbirth these levels fall to their normal situation and sometimes, together with the postpartum stress itself, a hair loss that occurs in the first six months after delivery. Although sometimes it can be spectacular, it is a reversible situation that normalizes naturally.

There are other specific causes that cause hair loss and that we must differentiate for a correct diagnosis and treatment.

Diffuse alopecia is a condition characterized by a loss of hair that is not concentrated in a specific area of the head. It responds to different reasons, some of the most frequent are infections, vitamin deficiency in the diet, aggressive pharmacological treatments or diseases of the thyroid gland. All these reasons affect the normal development of the hair follicle but reversibly, so that when the problem is solved the hair grows back normally. Therefore, it is important to diagnose the origin of alopecia and treat it properly in order to reverse the process.

It is a pathology that produces rounded areas of baldness, whose origin comes from a failure in the immune system that causes our defensive system to attack the hair follicles. It is frequently related to stress situations. Up to 40% of cases have previous anxiety crises. As it happens in diffuse if the stress situation is identified and solved, alopecia can be reversed.
We talk about alopecia total areata when it affects the entire scalp and alopecia areata universal when it affects the entire body.

It is produced by traction of the hair, in many cases, the result of an unconscious tic that makes us catch and stretch the hair. It can occur in both children and adults and is also called trichotillomania.
Occasionally, traumatic alopecia is caused by excessive traction of hairstyles such as bows or tails that continuously stretch the hair, leading to breakage and tearing.

It is a type of alopecia caused by an affectation of the dermis that prevents the growth of hair follicles. There are multiple causes but we can classify them as inherited, infectious, neoplastic or dermatosis. Also, it is the alopecia that is generated in an area where there has been a deep scar or wound on the skin, sometimes the result of a surgical intervention or a wound. This type of alopecia is usually permanent and does not respond to usual treatments.

It is a very rare alopecia to the point that it is considered a rare disease. It affects, above all, women and usually debuts at the stage of menopause but with a different pattern to androgenetic alopecia. Hair loss begins in the frontal area and is usually accompanied by hair loss in other areas of the body such as eyebrows and armpits.