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.

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.

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.

Folliculitis decalvans is an inflammation of the hair follicle that leads to bogginess or induration of involved parts of the scalp along with pustules, erosions, crusts, ulcers, and scale. It begins at a central point and spreads outward, leaving scarring, sores, and, due to the inflammation, hair loss in its wake. No permanent cure has been found for this condition. But there is promise in a regimen of dual therapy with Rifampin 300 mg twice daily and Clindamycin 300 mg twice daily. This new treatment can be used to control the condition, and tests have indicated that after 3 to 5 months long uninterrupted courses of treatment, many patients have seen limited to no recurrence.

Feline acne is a problem seen in cats primarily involving the formation of blackheads accompanied by inflammation on the cat's chin and surrounding areas that can cause lesions, alopecia, and crusty sores. In many cases symptoms are mild and the disease does not require treatment. Mild cases will look like the cat has dirt on its chin, but the dirt will not brush off. More severe cases, however, may respond slowly to treatment and seriously detract from the health and appearance of the cat. Feline acne can affect cats of any age, sex or breed, although Persian cats are also likely to develop acne on the face and in the skin folds. This problem can happen once, be reoccurring, or even persistent throughout the cat's life.

Sebaceous glands are skin glands that produce oil and are mostly found in the skin of the chin, at the base of the tail, and in the eyelids, lips, prepuce, and scrotum. They are connected to hair follicles. In acne, the follicles become clogged with black sebaceous material, forming comedones (also known as blackheads). Comedones can become irritated, swollen, infected, and ultimately pustules. These may elicit itching and discomfort due to swelling and bacterial growth inside infected glands. Cats may continue to scratch and reopen wounds, allowing bacterial infections to grow worse. Bacterial folliculitis occurs when follicules become infected with "Staphylococcus aureus", and commonly associated with moderate-to-severe feline acne. Secondary fungal infections (species "malassezia") may also occur.

Other conditions that can cause similar-appearing conditions include skin mites, ringworm, yeast infection, or autoimmune diseases such as eosinophilic granuloma complex ("rodent ulcers"). These can be ruled out by a simple biopsy of affected cells.

Feline acne is one of the top five most common skin conditions that veterinarians treat.

In both healthy and immunocompromised hosts, Majocchi's granuloma often presents as nodules and papules on areas that are most exposed to mechanical abuse—wear and tear—such as the upper and lower extremities. Patients will complain about papules, pustules, or even plaques and nodules at the site of infection. The papules will be pink-red and will be located in a perifollicular location. Hair shafts can be easily removed from the pustules and papules. Itching is also very common. Firm or fluctuant subcutaneous nodules or abscesses represent a second form of MG that is generally observed in immunosuppressed hosts. Nodules may develop in any hair-bearing part of the body but are most often observed on the forearms, hands, and legs of infected individuals. Involvement of the scalp and face is rarely observed. Lesions start as solitary or multiple well-circumscribed perifollicular papulopustules and nodules with or without background erythema and scaling. In rare circumstances, the lesions may have keloidal features.

Acneiform eruptions are a group of dermatoses including acne vulgaris, rosacea, folliculitis, and perioral dermatitis. Restated, acneiform eruptions are follicular eruptions characterized by papules and pustules resembling acne.

The hybrid term "acneiform", literally, refers to an appearance similar to acne.

The terminology used in this field can be complex, and occasionally contradictory. Some sources consider acne vulgaris part of the differential diagnosis for an acneiform eruption. Other sources classified acne vulgaris under acneiform eruption. MeSH explicitly excludes perioral dermatitis from the category of "acneiform eruptions", though it does group acneiform eruptions and perioral dermatitis together under "facial dermatoses".

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.

Pseudofolliculitis barbae (PFB), also known as barber's itch, folliculitis barbae traumatica, razor bumps, scarring pseudofolliculitis of the beard, and shave bumps, is a medical term for persistent irritation caused by shaving. Pseudofolliculitis barbae was first described in 1956.

Bacterial skin infections include:

- Folliculitis is an infection of the hair follicle that can resemble pimples.

- Impetigo is a highly contagious bacterial skin infection most common among pre-school children. It is primarily caused by "Staphylococcus aureus", and sometimes by "Streptococcus pyogenes".

- Erysipelas is an acute streptococcus bacterial infection of the deep epidermis with lymphatic spread.

- Cellulitis is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin. Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken: cracks in the skin, cuts, blisters, burns, insect bites, surgical wounds, intravenous drug injection or sites of intravenous catheter insertion. Skin on the face or lower legs is most commonly affected by this infection, though cellulitis can occur on any part of the body.

Pyoderma means any skin disease that is pyogenic (has pus). These include superficial bacterial infections such as impetigo, impetigo contagiosa, ecthyma, folliculitis, Bockhart's impetigo, furuncle, carbuncle, tropical ulcer, etc. Autoimmune conditions include pyoderma gangrenosum. Pyoderma affects more than 111 million children worldwide, making it one of the three most common skin disorders in children along with scabies and tinea.

Majocchi's disease (also known as Majocchi's Granuloma, "Purpura annularis telangiectodes,", and "Purpura annularis telangiectodes of Majocchi") is well-recognized but uncommon skin condition characterized by purple/bluish-red 1- to 3-cm annular patches composed of dark red telangiectases with petechiae. The name Majocchi's comes from the Professor Domenico Majocchi who first discovered the disorder in 1883. Domenico Majocchi was a professor of dermatology at the University of Parma and later the University of Bologna. Majocchi's disease can be defined as an infection of the dermal and subcutaneous tissues due to a fungal mold infection on the cutaneous layer of the skin. The most common dermatophyte is called "Trichophyton rubrum." This disease can affect both immunocompetent and immunocompromised hosts. However, immunocompromised individuals have a higher risk.

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".

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.

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.

Nematode dermatitis is a cutaneous condition characterized by widespread folliculitis caused by "Ancylostoma caninum".

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.

This disease in humans is usually caused by "Demodex folliculorum" (not the same species affecting dogs) and is usually called demodicosis which may have a rosacea-like appearance. Common symptoms include hair loss, itching and inflammation. An association with pityriasis folliculorum has also been described.

Demodicosis is most often seen in folliculitis (inflammation of the hair follicles of the skin). Depending on the location it may be a small pustules (pimples or pustules) at the exit of hair, placed on inflamed, congested skin. Demodicosis is accompanied by itching, swelling and erythema of the eyelid margins, the appearance of scales at the base of the eyelashes. Typically, patients complain of eyestrain. Characteristic of view of the affected century: plaque on the edge of the eyelids, eyelashes stuck together, surrounded by crusts as a clutch.

Symptoms include rash, itching skin, and hair which remains in spite of shaving. The site of the ingrown hair will form a reddish, raised bump, similar in appearance to a pimple.

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.

Main symptoms that occur when affected with Tinea Barbae is pimple or blister amongst affected area, swelling and redness around infected area, red and lumpy skin on infected area. Crusting around hairs in infected area will occur, hairs on infected area will also be effortless to pull out. Tinea Barbae can be itchy or painful to touch but these symptoms do not always occur.

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

Eosinophilic folliculitis (also known as "Eosinophilic pustular folliculitis" and "Sterile eosinophilic pustulosis") is an itchy rash with an unknown cause that is most common among individuals with HIV, though it can occur in HIV-negative individuals where it is known by the eponym Ofuji disease. EF consists of itchy red bumps (papules) centered on hair follicles and typically found on the upper body, sparing the abdomen and legs. The name eosinophilic folliculitis refers to the predominant immune cells associated with the disease (eosinophils) and the involvement of the hair follicles.

It is important to continue to watch for symptoms and signs of active disease during and after treatment to ensure that the disease is responding adequately and has not re-activated after therapy has been discontinued. Response to therapy may be indicated by the resolution of scalp symptoms such as itching, pain, tenderness, or burning, by improvement in the signs of scalp inflammation such as decreased redness, scaling or pustules, and by halting or slowing the progression of hair loss. A dermatologist can follow your cicatricial alopecia using these guidelines, and with the pull test. Photographs of the scalp may be useful in monitoring the course of the disease and response to treatment.

Boils are bumpy, red, pus-filled lumps around a hair follicle that are tender, warm, and very painful. They range from pea-sized to golf ball-sized. A yellow or white point at the center of the lump can be seen when the boil is ready to drain or discharge pus. In a severe infection, an individual may experience fever, swollen lymph nodes, and fatigue. A recurring boil is called chronic furunculosis. Skin infections tend to be recurrent in many patients and often spread to other family members. Systemic factors that lower resistance commonly are detectable, including: diabetes, obesity, and hematologic disorders. Boils can be caused by other skin conditions that cause the person to scratch and damage the skin.

Boils may appear on the buttocks or near the anus, the back, the neck, the stomach, the chest, the arms or legs, or even in the ear canal. Boils may also appear around the eye, where they are called styes. A boil on the gum is called intraoral dental sinus, or more commonly, a gumboil.