Simplified, you can imagine the hair follicle as a thread-like invagination in the skin, which is surrounded by special concentric cell layers. Coming from the outside in, these layers comprise an outer epithelial hair root sheath, also called stratum basale, a unicellular cell layer, the so-called "companion layer", and an inner epithelial hair root sheath, which in turn can be divided into three further layers. These are called Henle layer, Huxley layer and cuticle coming from outside. The bottom of the hair follicle is formed by the hair bulb, also known as hair bulb, while the roof of the hair follicle is called hair funnel or infundibulum.
The complete hair follicle is surrounded by a layer of connective tissue, which embeds it in the surrounding tissue and makes it movable against it. The outer epithelial hair root sheath is composed of several layers of cells that are rich in glycogen and provide important nutrients for hair growth. These cells are not horned in the area of the entire hair ball. At the seamless transition to the epidermis, the epidermis, the cells of this layer are now horny. The unmotivated "companion layer" is connected to the already hardened Henle layer via numerous desmosomes, adhesive contacts between the cells.
The companion layer, along with the entire inner epithelial hair root sheath, slides on the outer epithelial hair root sheath to the surface where it is abraded to release the hair. This complex of layers serves as anchoring in the hair, as the side of the cuticle facing the hair has barb-like structures on its surface. The hair bulb is slightly flared and contains the so-called matrix cells and melanocytes. Matrix cells are very divisive cells that are not horny at first and in the later keratinized state make up the majority of the hair. Melanocytes are cells that produce pigment and significantly define hair color. This pigment is released to the matrix cells, allowing it to reach the tip during hair growth.
The hair funnel is the opening of the hair follicle for the hair. This way it reaches the surface and can grow unhindered. Into the hair funnel open a sebaceous gland and a sweat gland. Just below the sebaceous gland, a small muscle inserts on the connective tissue root sheath, which can raise the hair of the body to goose bumps.
An abscess of the entire hair follicle is called boils. If it comes to the merger of several boils this is called carbuncle. This abscess can form on any hairy part of the body. However, they are especially common on the neck, nose, chest, armpits, groin, buttocks and inner thighs. Also for the external auditory canal is described such an accumulation. A boil is characterized by a central pus that is surrounded by a concentric reddened area that is painful to pressure. A carbuncle has a larger pus and is characterized by a greater pain.
The cause of an abscess on the hair follicle is usually an infection with Staphylococcus aureus, a bacterium, or a mixed infection of several bacterial species. In addition to bacteria but also trivial causes come into question. Often blame is too tight or abrasive clothing as well as bad hygiene after a shave. Since a boil or a carbuncle is potentially life-threatening, medical advice should be sought in case of a boil, provided that the abscess can not be emptied without outside help. In any case, sepsis threatens, which is why the doctor removes the pus and possibly treated with antibiotics. Carbuncle are particularly dangerous in the area of the oral cavity, as the germs quickly enter the brain via the bloodstream or the lymph. Special attention can be paid to hygiene and loose-fitting clothing for people with abscesses. As a result, a new appearance is significantly reduced.
Inflammation of the hair follicle is called folliculitis. This is noticeable by a reddening and slight pain in the area of one or more hairs. In contrast to an abscess of the hair follicle, inflammation of the hair follicle affects only the upper parts (infundibulum). If this is clogged by horny material, which spreads the inflammation on the entire hair follicle, it is called a boil, so an abscess of hair follicles. Risk factors of a hair follicle inflammation are diseases such as diabetes mellitus and acne, but also a therapy with cortisone ointments or a strong hairiness. This especially applies to men with strong beard growth. In addition, such inflammation often occurs in immunocompromised patients.
The cause of the inflammation may be like an abscess of bacterial cause. Furthermore, viruses and fungi come into question as a cause. As a rule, inflammation of the hair follicle is unproblematic. Although the redness in the area of the hair is often perceived as unaesthetic, it should regress within a few days. In a few cases, an inflammation causes a boil. The danger here is the development of life-threatening sepsis. Therefore, if in doubt, seek medical attention if a painful pus develops.
Recurrent inflammation of a hair follicle can cause scarring. In severe cases, the cause of the inflammation is treated, that is locally applied an ointment against the inflammation, the bacteria or fungi. Suspected spread to the body may also result in systemic therapy. Recently, phototherapy is offered as an alternative. The affected area is irradiated with UV light for approx. 15 minutes. As a home remedy for mild inflammation has proven treatment with chamomile.