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Origine et causes des poils incarnés.

Everything you need to know about the origin of ingrown hairs.

Ingrown hairs can sometimes be painful and may lead to infections, thus complicating the daily lives of those affected. But what are the origins of ingrown hairs? Elements of response in this article.

Summary
Published February 19, 2024, by Sandrine, Scientific Editor — 4 min read

What is an ingrown hair?

Before explaining what an ingrown hair is, it is necessary to recall where hairs come from. Indeed, with the exception of hairless areas (palms of hands, soles of feet, eyelids, inner sides of fingers, etc...), our entire body is equipped with hair follicles or pilo-sebaceous follicles. The lower part of the hair follicle is made up of the bulb, and it includes the hair matrix containing keratinocytes and melanocytes that produce hairs. The hairs travel through the hair canal and exit at the opening of the hair canal (ostium) to end up on the skin's surface.

An ingrown hair is a hair that has deviated from its usual path by growing under the skin. Indeed, it has not managed to pierce the epidermis and continues to grow under the skin, potentially causing inflammation and small red bumps that can itch. Sometimes, the ingrown hair can become infected and accompanied by pus, becoming painful. Certain areas are more affected by this phenomenon than others. In men, they primarily develop on the chest, chin, and neck (pseudo-folliculitis of the beard), whereas in women they are particularly observed on the legs, underarms, and pubic area.

Ingrown Hairs: What are the Risk Factors?

  • Inadequate shaving or hair removal techniques.

    The primary cause and main reason is shaving or hair removal.Indeed, certain hair removal and shaving techniques increase the risk of deviation and development of ingrown hairs, this is the case with double or triple blade shaving and root hair removal.

    When shaving is done against the direction of hair growth (for example, moving up the leg), especially with a multi-blade razor, the hair is more likely to become ingrown as it regrows.

    For root hair removal (waxing or using an epilator), the hair is pulled out from its root in the opposite direction of its growth. The hair also tends to deviate from its natural path, encouraging it to grow under the skin outside of its natural exit ostium.

  • The condition of the skin.

    Dry and thickened skin tends to prevent hair from emerging properly.

  • The nature of hairiness.

    A curly or coiled (corkscrew-like) hair is more likely to become ingrown due to its shape than a straight hair.

  • The thickness of the hair.

    The thicker a hair is, the more difficulty it will have penetrating the skin. Just like curly or kinky hair, a thick hair is therefore more at risk of becoming ingrown.

  • The pressure on the skin.

    The beard, legs, underarms, or bikini area are the zones where the risk of ingrown hairs is most significant, as these are areas frequently subjected to hair removal and/or shaving, and to repeated friction from tight clothing. This substantial pressure leads to a thickening of the skin. However, the thicker the skin, the greater the risk of ingrown hairs, as the hair struggles to break through.

Source:

  • WONG S. Y. & al. Preparing the hair follicle canal for hair shaft emergence. Experimental Dermatology (2021).

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