1. Introduction

As the largest organ in the body, the skin’s ability to protect against viruses, control body temperature, and detect touch is among its most crucial capabilities. The epidermis, dermis, and hypodermis are the three primary layers of skin. Numerous issues, including cancer, acne, wrinkles, and rashes, can affect the skin [1].

1.1 What is skin?

The largest organ of the body, the skin is composed of water, protein, fat, and minerals. It controls body temperature and shields your body from pathogens. Skin nerves enable us to experience emotions like heat and cold. The skin, along with hair, nails, sebaceous glands, and sweat glands, is a component of the entire system. The term “skin” refers to the body’s outer layer [2, 3].

1.2 What are the layers of skin?

The skin consists of three layers of tissue [4]:

Epidermis (top layer)
Dermis (middle layer)
Hypodermis (lower or fatty layer) (Figure 1)

1.3 What does the epidermis (top layer of skin) do?

Your epidermis is the top layer of your skin that you can see and touch. Keratin, a protein inside skin cells, makes up the skin cells and, together with other proteins, sticks together to form this layer [6, 7, 8].

Epidermis:

Serves as a barrier of protection: The epidermis serves as a barrier to stop bacteria and germs from infecting your body and bloodstream. In addition, it shields from the sun, rain, and other elements.
Creates new skin: The epidermis continually generates fresh skin cells. Your body eliminates about 25.000–40.000 old skin cells per day, which are replaced by these new ones. Every 30 days, your skin is renewed [6, 7, 8].
Safeguards your body: The epidermis contains Langerhans cells, which are a component of the immune system. Infections and bacteria are fought off by them.
Provides skin color: Melanin, the pigment that gives skin its color, is found in the epidermis. The color of your skin, hair, and eyes depends on how much melanin you have. The skin tone and rate of tanning are darker in those with more melanin production [6, 7, 8].

1.4 What is the dermis (middle layer of the skin) for?

The dermis makes up 90% of the skin thickness. This middle layer of skin

Contains collagen and elastin: Collagen is a protein that makes skin cells strong and durable. Elastin, another protein found in the dermis, keeps the skin supple. It also helps stretched skin to take its old shape.
Grows hair: The roots of the hair follicles are connected to the dermis.
Keeps you in touch: Nerves in the dermis let you know when something is too hot, itchy, or too soft to touch. These nerve receptors also help you feel pain.
Makes oil: Sebaceous glands in the dermis help keep the skin soft and smooth. Oil also prevents your skin from absorbing too much water when you swim or get caught in a rainstorm.
Produces sweat: Sweat glands in the dermis release sweat through the skin pores. Sweat helps regulate your body temperature.
Produces blood: Blood vessels in the dermis supply nutrients to the epidermis, keeping the skin layers healthy [1, 2, 3, 4, 5, 6, 7, 8, 9].

1.5 What does the hypodermis (bottom layer of the skin) do?

The bottom layer of the skin, or hypodermis, is the fatty layer. Hypodermis:

Cushions muscles and bones: The fat in the hypodermis protects muscles and bones from injury when you fall or have an accident.
Connective tissue: This tissue connects layers of skin to muscles and bones.
It helps nerves and blood vessels: Nerves and blood vessels in the dermis (middle layer) grow in the hypodermis. These nerves and blood vessels branch out to connect the hypodermis to the rest of the body.
It regulates body temperature: The fat in the hypodermis prevents you from getting too cold or hot [1, 2, 3, 4, 5, 6, 7, 8, 9].

2. Skin abscess

Skin abscesses are caused by the accumulation of pus in the dermis or subcutaneous tissue and have a swollen, red, tender, fluctuating appearance, often accompanied by surrounding cellulitis [10]. The diagnosis of skin abscesses is based on physical examination, but rarely an ancillary technique such as ultrasonography may be used.

Healthy human skin has many physiologic barriers against microorganisms. The stratum corneum provides mechanical protection with its covering layer. Desquamation, which develops as a result of the skin’s continuous self-renewal, also provides the removal of colonized bacteria.

Skin abscess formation is of two types: under the skin or above the skin. Although skin abscesses affect people of all ages, they are usually caused by bacterial infection. Bacterial infections of the skin are among the most common infections in the community. Roughly 20% of outpatients in dermatology outpatient clinics are diagnosed with bacterial skin infections. Skin abscess formation can occur anywhere on the body. The treatment of bacterial skin infections, defined as pyoderma, can be simple drainage or severe enough to require intensive care conditions, sometimes even resulting in death [11, 12, 13].

The most frequently isolated pathogenic microorganisms in bacterial skin infections are Staphylococcus aureus and Streptococcus pyogenes. Cutaneous and superficial abscesses are the most common skin diseases seen by physicians. In parallel with the increase in community-acquired MRSA (Methicillin-Resistant S. aureus) infections, the incidence of skin abscesses has also increased. MRSA infection is the most common cause of skin abscesses [11, 12, 13].

Many bacteria may be responsible for the formation of skin abscesses. When evaluated under main groups, it can be classified as infection of gram-positive bacteria, gram-negative bacteria, and other microorganisms. As a result, many diseases with different clinical presentations and courses are observed in the skin. However, the most common factors observed in abscesses are streptococci and staphylococci, which are gram-positive bacteria.

2.1 Classification

Different classifications can be made in its simplest form;

Light
Middle
Severe.

2.2 Risk factors

Risk factors can be skin-related or systemic diseases. In addition, other factors such as diet, clothing habits, and cleaning habits may also predispose to infections. The most common skin-related factors are, of course, conditions that disrupt the integrity of the skin such as incisions, burns, trauma, and insect bites. Again, in itchy skin diseases such as atopic dermatitis and contact dermatitis, the loss of the protective function of the skin due to erosions caused by scratching may prepare the ground. Skin diseases such as chickenpox and pemphigus, in which the integrity of the skin is lost, also pose a risk [14]. Other risk factors are given in the Table 1.

Trauma
Steroid therapy
Chemotherapy
Chronic Diseases (DM, morbid obesity, malignancy, etc.)
Immune Deficiencies (AIDS etc.)
Sickle cell disease
Peripheral vascular disorders, vascular insufficiency (lymphatic, venous)
Inflammatory Bowel Diseases (Crohn’s disease, Ulcerative colitis)
Serious burns
Alcoholism
IV drug use
Poor hygiene
Some Chronic diseases
Animal or human bites
Fungal infections of the skin
Organ Failures (liver/kidney failure)
Surgical procedures that disrupt lymphatic drainage
Fever above 38°C in infants

Table 1.

Risk factor [14].

2.3 Abscess symptoms

A hard or palpable soft swelling under the skin
Pain and tenderness in the affected area
Increased temperature and redness in the same area
Visible accumulation of white or yellow infectious material under the skin
Systemic fever
Tremor

2.4 Types of skin abscess

There is a confusion in the definition of skin abscess. In many places in the literature, bacterial infections of the skin are also examined under this title. However, in this article, we will talk about lesions and conditions with abscess clinics. Among these, folliculitis, furuncle, and carbuncle are related to the skin and we will also mention pilonidal abscesses that can be considered as skin abscesses.

2.5 Differential diagnosis of skin abscess

Chickenpox; Varicella
Herpetic İnfections
Ruptured Epidermoid cyst
Hidradenitis Suppurativa
Skin Tuberculosis
Deep fungal infections
Lymphadenitis
Pilonidal Sinus Infection

3. Folliculitis

Folliculitis is an inflammation of the hair follicles. Anywhere there is hair on our body, it can grow there. It is a typical skin condition. Since it frequently does not require medical attention and might disappear on its own, it is challenging to determine the exact incidence. Usually, a simple skin inspection is sufficient for diagnosis. Sometimes it is possible to perform a culture and antibiogram.

An injury or irritant may be the cause (infection or non-infection). Bacterial or non-bacterial (viral, fungal, parasitic) infectious folliculitis can develop in either the superficial or deep region of the hair follicle. Normal causes of non-infectious folliculitis include follicular damage or blockage. They are painful sores that frequently contain pus. When the inflammation around the hair follicles deepens, a boil develops [15, 16, 17].

Most frequently, the bacterium S. aureus is the responsible party. Multiple groups of tiny, elevated, itchy, erythematous papules, often less than 5 mm in diameter, are the hallmarks of bacterial folliculitis. The onset is frequently acute, and pustules may be visible.

Depending on which area of the hair follicle is affected, folliculitis can either be superficial or profound. Neutrophils invading the area around the hair follicle is typically a sign of acute bacterial folliculitis. Neutrophils are restricted to the infundibulum in superficial folliculitis; in deep folliculitis, they invade the deeper portion of the follicle and the surrounding dermis. Later stages of the lesions display persistent granulomatous inflammation with enormous cells that contain fragments of hair and keratin. In general, infectious folliculitis is more susceptible to therapy than folliculitis brought on by non-infectious reasons, and superficial folliculitis is easier to treat than deep folliculitis.

It is important to distinguish between bacterial folliculitis and other infectious causes of facial folliculitis, such as viruses, fungi, and parasites, such as Demodex folliculorum, as well as bacteria like Candida and Pityrosporum. We must take into account the etiology, severity, and anatomical distribution when handling folliculitis. Warm normal saline compresses (one teaspoon table salt to two cups tap water) used topically, followed by bacitracin or erythromycin ointment and sterile absorbent gauze bandages, are effective treatments for many types of folliculitis. A 7–10 day regimen of oral erythromycin (250–500 mg/day for adults and 30–50 mg/kg/day in evenly divided groups) may be used for moderate S aureus infections [15, 16, 17] (Figure 2).

4. Furuncle—carbuncles

A furuncle is an infection of the hair follicles that spreads to the surrounding skin and underlying deep subcutaneous tissue. They often present as a painful, swollen lump covered in many sinus tracts or pustules. A contiguous group of two or more furuncles is known as a carbuncle. Regional lymphadenopathy is a possibility, and systemic symptoms are typically present. Although they can appear on any area of the body with hair, they are more frequently found in places with thick skin, such as the back of the neck, the back, and the thighs. There may be one or several carbuncles [18, 19].

Bacteria can enter the sebaceous gland duct and hair follicle, resulting in clinical symptoms ranging from a straightforward infection to a serious and life-threatening condition. Carbuncles are brought on by a bacterial infection of the hair follicle. S. aureus is the most frequent culprit and frequently includes methicillin-resistant S. aureus. Sometimes, particularly in recurring cases involving the anogenital region, anaerobic bacteria might be the source of carbuncles.

On typically healthy skin, S. aureus can be discovered, most frequently in intertriginous regions like the groin, axillae, buttocks, and neck. Additionally, the nostrils may also contain it. Scratching can spread S. aureus to several anatomical locations. Bacteria can infect the hair follicle when the skin’s protective barrier is breached. The bacteria can grow after being inoculated and result in folliculitis, boils, and/or carbuncles.

4.1 Who is more likely to have a froncle/carbuncle?

Elderly
Obese
People with diabetes
Individuals with weak immune systems
People living in poor hygienic conditions
People living in hot and humid climates
People with chronic skin diseases
People with kidney and liver disease

They are mostly found in young to middle-aged adults and are rare in early childhood. Carbuncles are known to affect men more than women. Disruption of the skin barrier can be caused by eczema, diabetes, alcohol abuse disorder, malnutrition, immune deficiency, obesity, and poor hygiene [20] (Figure 3).

4.2 Diagnosis

A patient presenting with a carbuncle typically has a history of a tender nodule that grows slowly. According to the patient, the lesion initially appeared as a “pimple” or pustule that they attempted to pop, but over the course of a few days to weeks, it grew increasingly larger. It is well recognized that carbuncles can induce systemic symptoms, but this is not necessary for diagnosis. Regional lymphadenopathy, fever, tiredness, and malaise are examples of systemic symptoms.

Carbuncles are often diagnosed based on the results of a physical examination. It’s crucial to collect a bacterial culture and sensitivity test from the purulent fluid contained within the carbuncle when one is suspected of having one. Before beginning antibiotic treatment, a bacterial swab should be done. To direct antibiotic therapy and rule out MRSA or any other gram-negative bacteria as the cause of the illness, bacterial cultures, and sensitivities are crucial [16, 17, 18, 19, 20].

4.3 Treatment

The patient should be provided with rest and monitored at short intervals. Typically, carbuncles necessitate both medicinal and surgical treatment. Typically, carbuncles are drained and incised while under local anesthetic. If the abscess is immature, on the other hand, a warm dressing is used to assist it in developing before an incision is made to drain the adult abscess. It is common to utilize antiseptics, antibiotic creams, oral broad-spectrum antibiotics, and analgesics.

Typically, oral antibiotics are started following incision and drainage. Dicloxacillin and cephalosporins are typical first-line oral antibiotics. Oral antibiotics such as clindamycin, tetracyclines, trimethoprim-sulfamethoxazole, linezolid, or glycopeptide may be taken if MRSA is suspected or cultivated. As an additional treatment, topical antibiotics like clindamycin or mupirocin may be applied.

Septicemia, cavernous sinus thrombophlebitis, and scarring are possible side effects of carbuncles. Patients must be given information on how to avoid developing carbuncles, including how to maintain excellent hygiene, lose weight, manage their diabetes, eat well, and receive suitable treatment for any underlying illnesses or immunological deficiencies. Furthermore, by administering mupirocin to the interior nostrils twice daily for 12 to 30 days, staphylococcal decolonization of the nostrils can be accomplished [18, 19, 20, 21].

5. Approach to recurrent conditions

Local causes related to the site of infection should be reviewed [20];
If there is the presence of foreign body, pilonidal cyst, hidradenitis suppurativa, etc., treatment for these conditions
Abscess must be drained
In recurrent abscesses, culture should be taken and a 5–10-day treatment should be organized with an antibiotic that is effective for the isolated pathogen.
Personal hygiene and decontamination can be performed
Intranasal treatment can be given

6. Conclusion

The exact incidence of skin abscesses is unknown. Because the patient may go from a minor illness to a situation that can lead to death. When the clinician detects an abscess on the skin, he/she should observe it closely and start antibiotic therapy if necessary. It should not be forgotten that a small, oversimplified abscess focus may cause trouble for the patient and the physician for months. At the same time, patients should also consult a physician.

Diogo Soga

Chapters authored

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