Most carbuncles, boils, and other cases of folliculitis develop from "Staphylococcus aureus".

Folliculitis starts with the introduction of a skin pathogen to a hair follicle. Hair follicles can also be damaged by friction from clothing, an insect bite, blockage of the follicle, shaving, or braids too tight and too close to the scalp. The damaged follicles are then infected by "Staphylococcus". Folliculitis can affect people of all ages.

Iron deficiency anemia is sometimes associated with chronic cases.

Although the exact cause of feline acne is unknown, some causes include:

- Hyperactive sebaceous glands

- Poor hygiene

- Stress

- Developing secondary to fungal, viral, and bacterial infections

- Reaction to medication

- Drinking from plastic containers to which the cat is allergic

- Demodicosis or mange, causing itchiness and hair loss

- Suppressed immune system

- Hair follicles that don't function properly

- Rubbing the chin (to display affection or mark territory) on non-sanitized household items

- Hormonal imbalance

- Contracting the infection from other cats in the same household

Folliculitis is the infection and inflammation of one or more hair follicles. The condition may occur anywhere on the skin except the palms of the hands and soles of the feet. The rash may appear as pimples that come to white tips on the face, chest, back, arms, legs, buttocks, and head.

The transmission of Tinea Barbae to humans occurs through contact of an infected animal to the skin of a human. Infection can occasionally be transmitted through contact of infected animal hair on human skin. Tinea Barbae is very rarely transmitted through human to human contact but is not completely impossible.

Fungal skin infections may present as either a superficial or deep infection of the skin, hair, and/or nails. As of 2010, they affect about one billion people globally.

Dempster-Shafer Theory is used for detecting skin infection and displaying the result of the detection process.

Eosinophilic folliculitis associated with HIV infection typically affects individuals with advanced HIV and low T helper cell counts. It affects both men and women as well as children with HIV and is found throughout the world.

EF may also affect individuals with hematologic disease such as leukemia and lymphoma. It may also affect otherwise normal infants in a self-limited form. HIV-negative individuals can also develop EF — this is more common in Japan.

Hot tub folliculitis (also known as "Pseudomonas aeruginosa" folliculitis) is a common type of folliculitis, a condition which causes inflammation of hair follicles.

This condition is caused by an infection of hair follicles due to the bacterium "Pseudomonas aeruginosa". The bacterium is commonly found in hot tubs, water slides, and such places. Children are more prone to this because they usually stay in the water longer than adults. Hot tub folliculitis appears on the skin in the form of a rash, roughly resembling chicken pox and then develops further to appear as a pimple. Hot tub folliculitis can be extremely painful and/or itchy, and left alone without scratching will go away much more quickly. If the rash is aggravated, it can stay, worsen, and spread, lasting for months. By that time, it is much more difficult to treat. The dots usually go away after about 7 to 10 days but the condition leaves a hyperpigmented lesion that goes away after a few months.

Normally, the rash does not need specific treatment and will go away on its own. Antibiotics may be prescribed in some cases. If the rash continues to appear longer than the 7- to 10-day time period, a physician should be consulted. Folliculitis that is not treated properly could worsen and cause abscesses.

Tinea barbæ (also known as "Barber's itch," "Ringworm of the beard," and "Tinea sycosis") is a fungal infection of the hair. Tinea barbae is due to a dermatophytic infection around the bearded area of men. Generally, the infection occurs as a follicular inflammation, or as a cutaneous granulomatous lesion, i.e. a chronic inflammatory reaction. It is one of the causes of Folliculitis. It is most common among agricultural workers, as the transmission is more common from animal-to-human than human-to-human. The most common causes are "Trichophyton mentagrophytes" and "T. verrucosum".

Prickly heat can be prevented by avoiding activities that induce sweating, using air conditioning to cool the environment, wearing light clothing and in general, avoiding hot and humid weather. Frequent cool showers or cool baths with mild soap can help to prevent heat rash.

The exact cause of Majocchi's granuloma is not well established however a dysfunctinoal immune system may be a causative factor. The first form of MG, the superficial perifollicular form occurs predominately on the legs of otherwise healthy young women who repeatedly shave their legs and develop hair follicle occlusions that directly or indirectly disrupt the follicle and allow for passive introduction of the organism into the dermis. Hence, the physical barrier of the skin is important because it prevents the penetration of microorganisms. Physical factors that play a major role in inhibiting dermal invasion include the interaction among keratin production, the rate of epidermal turnover, the degree of hydration and lipid composition of the stratum corneum, CO levels, and the presence or absence of hair. Keratin and/or necrotic material can also be introduced into the dermis with an infectious organism to further enhance the problem. In immunocompromised individuals, the use of topical corticosteroids may lead to a dermatophyte infection due to local immunosuppression.

Minor cases of demodectic mange usually do not cause much itching but might cause pustules on the dog's skin, redness, scaling, leathery, hair loss, warm to the touch, or any combination of these. It most commonly appears first on the face, around the eyes, or at the corners of the mouth, and on the forelimbs and paws. May be misdiagnosed as a "hot spot" or other skin ailment.

In the more severe form, hair loss can occur in patches all over the body and might be accompanied by crusting, pain, enlarged lymph nodes, and deep skin infections.

Demodectic mange is transmitted from host to host through direct contact. Typically animals become infected through nursing from their mother. Demodex mites are host-adapted; there is no zoonotic potential in either canine or feline demodicosis. These mites ("Demodex canis") thrive only on their specific hosts (dogs). The transmission of these mites from mother to pup is normal (which is why the mites are normal inhabitants of the dog's skin), but some individuals are sensitive to the mites due to a cellular immune deficiency, underlying disease, stress, or malnutrition, which can lead to the development of clinical demodectic mange.

Some breeds appear to have an increased risk of mild cases as young dogs, including the Afghan Hound, American Staffordshire Terrier, Boston Terrier, Boxer, Chihuahua, Chow Chow, Shar Pei, Collie, Dalmatian, Doberman Pinscher, Bulldog, French Bulldog, English Bull Terrier, Miniature Bull Terrier, German Shepherd Dog, Great Dane, Old English Sheepdog, American Pit Bull Terrier, West Highland White Terrier, Rat Terrier, Yorkshire Terrier, dachshund and Pug.

Miliaria occurs when the sweat gland ducts get plugged due to dead skin cells or bacteria such as "Staphylococcus epidermidis", a common bacterium that occurs on the skin which is also associated with acne.

The trapped sweat leads to irritation (prickling), itching and to a rash of very small blisters, usually in a localized area of the skin.

Demodectic mange also occurs in other domestic and wild animals including captive pandas and in China. The mites are specific to their hosts, and each mammal species is host to one or two unique species of Demodex mites. There are two types of demodectic mange in cats. "Demodex cati" causes follicular mange, similar to that seen in dogs, though it is much less common. "Demodex gatoi" is a more superficial form of mange, causes an itchy skin condition, and is contagious amongst cats.

Razor burn is a less serious condition caused by shaving, characterized by mild to moderate redness and irritation on the surface of the skin. Unlike PFB, it is usually transient and there is no infection involved.

There is also a condition called "folliculitis barbae". The difference between the two is the cause of the inflammation in the hair follicles. Folliculitis barbae is caused by viral or bacterial infections, where pseudofolliculitis is caused by irritation from shaving and ingrown hairs.

A related condition, pseudofolliculitis nuchae, occurs on the back of the neck, often along the posterior hairline, when curved hairs are cut short and allowed to grow back into the skin. Left untreated, this can develop into acne keloidalis nuchae, a condition where hard, dark keloid-like bumps form on the neck. Both occur frequently in black men in the military, where it is so common that services often have widely known protocols for management

Superficial pustular folliculitis (also known as "Impetigo of Bockhart" and "Superficial folliculitis") is a superficial folliculitis with thin-walled pustules at the follicular openings.

Irritant folliculitis is a cutaneous condition and usually occurs following the application of topical medications.

Fiddler’s neck does not usually form unless the musician is practicing or playing for more than a few hours each day, and only seems to develop after a few years of serious playing. Thus, when not infected or otherwise problematic, fiddler’s neck may be known as a benign practice mark and may be worn proudly as an indication of long hours of practice. Blum & Ritter (1990) found that 62% of 523 professional violinists and violists in West Germany experienced fiddler’s neck, with the percentage among violists being higher (67%) than among violinists (59%). Viola players are believed to be more predisposed to developing fiddler’s neck than violinists because the viola is larger and heavier, but this has not been empirically confirmed.

The development of fiddler’s neck does not depend on preexisting skin problems, and Blum & Ritter find that only 23% of men and 14% of women in their study reported cutaneous disorders in other parts of the face (mainly acne and eczema) that were independent of playing the violin or viola. Fiddler’s neck may exacerbate existing acne, but acne may also be limited solely to the lesion and not appear elsewhere. Nonetheless, musicians with underlying dermatologic diseases like acne and eczema are more endangered by fiddler’s neck than others. Males may develop folliculitis or boils due to involvement of beard hair.

Placing the cat's water in a shallow dish may prevent the chin from absorbing the bacteria in the water while the cat is drinking. If the cat is allergic to plastics or dyes, using a stainless-steel or glass dish is recommended . Cats may also have food allergies that make the development of acne more likely, so that switching kibble, or changing to a hydrolysed diet may be effective. Maintaining good hygiene and grooming habits make the development of feline acne less likely. Washing and exfoliating the chin with a gentle benzoyl-peroxide solution also may be preventive of further outbreaks.

Eosinophilic pustular folliculitis of infancy (also known as "Eosinophilic pustular folliculitis in infancy," "Infantile eosinophilic pustular folliculitis," and "Neonatal eosinophilic pustular folliculitis") is a cutaneous condition characterized by recurrent pruritic crops of follicular vesiculopustular lesions.

Skin infections and wrestling is the role of skin infections in wrestling. This is an important topic in wrestling since breaks in the skin are easily invaded by bacteria or fungi and wrestling involves constant physical contact that can cause transmission of viral, bacterial, and fungal pathogens. These infections can also be spread through indirect contact, for example, from the skin flora of an infected individual to a wrestling mat, to another wrestler. According to the National Collegiate Athletic Association's (NCAA) Injury Surveillance System, ten percent of all time-loss injuries in wrestling are due to skin infections.

There is no certainty about the cause of this disorder, but it is known that the bacterium Staphylococcus aureus has a central role. This bacterium can be detected in the lesions of most patients. It is unclear if a primarily sterile infection with secondary colonization by Staphylococcus aureus is present, or if this bactery itself leads at first to a strong immune reaction. Another possibility is that the toxins produced by this bacterium could act as superantigens that activate directly the T-cells over the variable domain of T-cell receptors. Nonetheless "Staphylococcus aureus" can by found in almost all patients affected by this disorder, while it is only seen in 20–30% of non-affected people.

As Staphylococcus aureus is not always found in people that suffer from folliculitis decalvans, other factors must be present. Through examinations in families it was found that there is a family connection to the occurrences, which leads to the conclusion that there is a genetic predisposition for it; for example, patients with folliculitis decalvans could have a hereditary different opening of the hair follicle that could facilitate the lodging of the bacteria. Immunologically, another possibility is that specially strong intercellular fixation protein ICAM-1 contributes to numerous inflammations with its strong effect of attracting neutrophiles such as granulocytes and lymphocytes.

Fungal folliculitis (also known as Majocchi granuloma) is a skin condition characterized by a deep, pustular type of tinea circinata resembling a carbuncle or kerion.

Other causes include poor immune system function such as from HIV/AIDS, diabetes, malnutrition, or alcoholism. Poor hygiene and obesity have also been linked. It may occur following antibiotic use due to the development of resistance to the antibiotics used. An associated skin disease favors recurrence. This may be attributed to the persistent colonization of abnormal skin with "S. aureus" strains, such as is the case in persons with atopic dermatitis.

Boils which recur under the arm, breast or in the groin area may be associated with hidradenitis suppurativa (HS).

The cause of EF is unknown. A variety of microorganisms have been implicated, including the mite Demodex, the yeast Pityrosporum, and bacteria. An autoimmune process has also been investigated.