Folliculitis, carbuncles, and furuncles: Nursing

Folliculitis is a superficial bacterial infection of the hair follicles, while furuncles, or boils, are deeper infections of the hair follicles and the surrounding tissue, and carbuncles are groups of two or more furuncles. They are usually caused by bacteria, but viruses, fungi, and parasites may also cause the infection.

Okay, let’s go over some physiology. Normally, the skin is divided into three layers, the epidermis, dermis, and hypodermis. The epidermis is the thin outermost layer of skin, the dermis is the thicker layer that lies below that, and the hypodermis is the lowest layer that’s made of fat and connective tissue and anchors the skin to the underlying muscle.

Now, hair, along with nails and skin glands, are considered skin appendages that help with regulating body temperature and protection from the environment. Hair is found on nearly every part of skin except the palms of the hands, soles of the feet, and the lips.

Every strand of hair is composed of the shaft, root, and bulb that sits in a pouch-like structure called the hair follicle. Next is the epidermal tissue that dips down into the dermis, and is associated with other structures like apocrine glands, sebaceous glands, the arrector pili muscle, and nerve receptors. Inside the bulb lies the hair matrix which serves as the active site of hair growth and gives hair its color.

Now, normally, the skin surface is colonized by a huge number of microorganisms that make up the normal skin flora. This flora consists mostly of bacteria, such as Staphylococcus epidermidis, as well as certain fungi, such as Candida albicans. The normal skin flora is typically non-pathogenic, meaning that these microorganisms don’t cause any disease. In fact, they are often beneficial, since they serve as a physical and competitive barrier that helps prevent pathogenic microorganisms from invading and infecting the skin and its appendages.

Now, folliculitis, furuncles and carbuncles are all typically caused by Gram positive pathogenic bacteria, with the most common one being Staphylococcus aureus. Less commonly, Gram negative pathogenic bacteria can also be involved, like Pseudomonas aeruginosa which loves humid or wet conditions, like hot tubs, and can cause a condition called hot tub folliculitis.

Risk factors that can allow these microorganisms to invade the skin appendages include having previous damage due to insect bites, minor trauma, abrasions, skin conditions like eczema, previous skin infections like impetigo or cellulitis; as well as using hot tubs or public pools. Additional risk factors include prolonged use of oral antibiotics; obesity, diabetes mellitus, or being immunocompromised.

Now, folliculitis occurs when pathogenic bacteria find a way to invade the hair follicle and cause infection of the superficial part of the follicle. On the other hand, furuncles occur when bacteria manage to affect the deeper part of the hair follicles and the surrounding tissue, while a carbuncle are groups of furuncles that develop in the same area.

In severe cases, these infections may cause complications, such as the formation of abscesses, as well as extensive tissue damage and necrosis, which can result in the formation of scars or dark spots in the skin. Another complication is the destruction of the hair follicles, which can lead to permanent hair loss. Lastly, if the infection spreads to the blood, it may result in sepsis.

Okay, moving onto clinical manifestations. Folliculitis develops anywhere there’s hair, but it's more common in the scalp, arm pit, or groin area, which are areas prone to friction and moisture. It typically presents as a tender or painless pustule with the hair shaft in its center. Other symptoms include minimal erythema, pruritus or tenderness. Eventually, the pustules tend to heal without any scarring or follicle loss. It is important to distinguish folliculitis from pseudofolliculitis, which is an inflammation of an ingrown hair usually on the face due to shaving and it’s also known as “razor burn”.

On the other hand, furuncles and carbuncles most commonly manifest on the lower abdomen, buttocks, and legs. Furuncles typically present as a deep-seated, firm, tender, erythematous perifollicular nodule. They are typically indurated, with central necrosis, and there can be draining pus. Constitutional symptoms are typically absent. In contrast, carbuncles present as clusters of painful, swollen and draining pustules, are often accompanied by fever, chills, and lymphadenopathy.

Now, the diagnosis of folliculitis, furuncles and carbuncles primarily involves the client’s history and physical assessment. There are no specific laboratory tests, but a complete blood count may reveal leukocytosis, as well as increased inflammatory markers like ESR and CRP. For furuncles and carbuncles, a gram stain and culture of the purulent exudate can be also performed to identify the causative organism.