How to Treat an Infected Ingrown Hair?

An ingrown hair most often manifests as small red bumps associated with local inflammation. In some cases, this skin reaction can progress to an infection of the hair follicle, called folliculitis. This is typically caused by bacterial proliferation, most often by Staphylococcus aureus, facilitated by a skin barrier compromised. Clinically, this presents as inflamed bumps sometimes filled with pus, painful to the touch, and persistent. In some cases, the infection may develop into a cyst following an ingrown hair, or even a localized abscess requiring medical treatment.

The hair removal technique strongly influences the occurrence of ingrown hairs.

Indeed, after shaving, flush-cut hairs develop a sharp tip. During regrowth, they can curl back and re-enter the epidermis instead of emerging through the skin surface, triggering a local inflammatory response. This situation creates an environment conducive to bacterial invasion and follicle infection. Other factors increase the risk of ingrown hair, notably hair type. Curly or kinky hair represents a major risk factor because of the acute angle it forms with the skin surface, facilitating its penetration back into the skin. Genetic predispositions have also been suggested, particularly KRT75 gene mutations, involved in the structure of the hair follicle.

The pathophysiology of an infected ingrown hair involves the hair invaginating into the epidermis, resulting in localized inflammation followed by infection when bacterial colonization occurs.

Scientifically, this phenomenon is described by the term Pseudofolliculitis barbae. It is a chronic inflammatory skin condition, frequently observed after shaving, particularly on the neck and cheeks, but also in areas subjected to regular hair removal, such as the bikini line. In these locations, an abscess of an ingrown hair in the bikini line or an abscess of an ingrown hair in the pubic area can arise due to hair density, local moisture, and repeated friction. It is characterized by papules and pustules secondary to hair ingrowth, which in some individuals may progress to scarring or keloids.

When faced with an infected ingrown hair, the first rule is to avoid puncturing the bump to drain the pus.

This manipulation, often performed with the fingers or a non-sterile object, facilitates the introduction of new bacteria into an already infected hair follicle. It can thus exacerbate local inflammation, prolong the infection’s duration, and increase the risk of complications, such as the formation of boils, which correspond to a deep infection of the pilosebaceous follicle.

Treatment relies primarily on appropriate hygiene measures. It is recommended to gently cleanse the affected area once or twice daily with lukewarm water and a mild cleanser to limit bacterial proliferation without further compromising the skin barrier. Daily application of a topical antiseptic may also be considered to reduce bacterial load.

In certain pronounced inflammatory cases, the healthcare provider may also recommend a topical corticosteroid cream for ingrown hairs to reduce inflammation and perifollicular edema. It is equally essential to suspend any form of hair removal or shaving on the affected area until the lesions have completely resolved, to avoid perpetuating the inflammation and the emergence of new follicular infections.

In most cases, the infection associated with an ingrown hair remains superficial and transient, with resolution in a few days. However, if lesions become very painful, spread, are accompanied by systemic signs, or progress to an abscess, a dermatology consultation is necessary. Depending on the severity, the physician may prescribe topical or oral antibiotics to control the bacterial infection. Other local approaches may also be proposed, such as benzoyl peroxide, which has antibacterial properties, or retinoids topical, which help normalize follicular keratinization and limit recurrences.

In certain cases, other therapeutic approaches may be considered. When infected ingrown hairs give rise to persistent pigmented spots, particularly in darker skin phototypes, the dermatologist may recommend the use of depigmenting agents such as hydroquinone. This compound works by inhibiting tyrosinase, a key enzyme in the melanin synthesis process, and allows for the gradual reduction of post-inflammatory hyperpigmentation.

In patients presenting with infected ingrown hairs that are frequent and resistant to conventional measures, particularly in the context of Pseudofolliculitis barbae, laser therapy represents a compelling long-term option. By targeting the hair follicle and reducing hair density and rigidity, the laser lowers the risk of subcutaneous regrowth and, consequently, the associated inflammatory and infectious phenomena.

Furthermore, especially in women, the use of topical eflornithine can also be recommended. This molecule inhibits ornithine decarboxylase, an enzyme involved in hair growth, thereby slowing hair regrowth. By reducing the frequency of shaving or hair removal, it indirectly helps limit ingrown hairs and associated follicular infections.

Finally, when infected ingrown hairs occur in the context of excessive or atypical hair growth, an endocrinological evaluation may be appropriate. A hormonal imbalance, notably hyperandrogenism, can promote dense, coarse hair, mechanically increasing the risk of ingrown hairs and chronic folliculitis.

In order to reduce the risk of ingrown hair infections, rigorous hygiene is indispensable, particularly when shaving or waxing. The razor should be thoroughly rinsed with warm water after each use to remove hair, skin debris, and microorganisms. It is also essential to change the blade regularly, as a dull blade promotes microcuts and bacterial proliferation. Moreover, the razor is strictly personal: sharing it or using someone else’s significantly increases the risk of bacterial transmission, especially of Staphylococcus aureus.

In addition, shaving too frequently, against the grain, or with excessive pressure promotes cutting the hair below the skin surface, thereby increasing the risk of ingrown hairs.

To limit the occurrence of ingrown hairs, we also recommend that you hydrate and exfoliate your skin regularly. Indeed, dry or thick skin promotes hair follicle blockage and prevents the hair from properly emerging at the skin surface. By caring for the skin barrier, you mechanically reduce the risk of ingrown hairs… and thus of infected ingrown hairs.

• FRIEDMAN A. J. & al. Pseudofolliculitis barbae in women: A clinical perspective. British Journal of Dermatology (2015).

• SCHWARTZ R. A. & al. Pseudofolliculitis cutis: A vexing disorder of hair growth. British Journal of Dermatology (2015).

• RASHMI S. & al. Ingrowing hair: A case report. Medicine (2016).

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