Skin Infections

Impetigo is a common bacterial infection of the superficial layers of the epidermis (the outermost layer of the skin) that is highly contagious and can spread easily. It most commonly presents as erythematous plaques with a yellow crust and may be itchy or painful.

It is mainly a disease of children between the ages of 2–5 and can be classified as non-bullous (70% of cases, presenting as small, itchy red sores around the nose/mouth that rupture and form a thick, golden-brown crust) or bullous (large, fragile, flaccid blisters that contain fluid). It typically manifests on the face but can also occur in other areas.Source: Impetigo | Health topics A to Z | CKS | NICE (opens in a new tab)

Diagnosis

Diagnosis is typically based on symptoms, clinical manifestations and patient demographics alone. Bacterial cultures from skin swabs are typically reserved for confirming the diagnosis in atypical presentations, managing refractory cases or checking for the presence of methicillin-resistant Staphylococcus aureus (MRSA).Source: Diagnosis | Diagnosis | Impetigo | CKS | NICE (opens in a new tab)

Treatment

Treatment is with the use of topical antibiotics +/- systemic antibiotics. For individuals with localised, uncomplicated, non-bullous impetigo, topical therapy alone is the treatment of choice. Systemic antibiotics should be prescribed for all cases of bullous impetigo, non-bullous impetigo with more than five lesions, deep tissue involvement or systemic signs of infection. While untreated impetigo is usually self-limiting within 14–21 days, antibiotics decrease the duration (within 10 days) and the spread of the cutaneous disease, as well as the chance of complications involving other areas of the body. Personal hygiene is important, with children regularly encouraged to wash their hands and avoid other children during the active outbreak.Source: Bullous impetigo | Management | Impetigo | CKS | NICE (opens in a new tab)

Cellulitis is a common bacterial infection of the skin, affecting both the dermis and subcutaneous tissue. It affects approximately 1 in 40 patients annually, with an equal distribution in men and women, typically seen in the middle-aged to elderly. It is most commonly caused by the bacteria Streptococcus pyogenes and Staphylococcus aureus. It usually manifests in the lower legs and feet and has a unilateral presentation, with bilateral cellulitis being rare.Sources: Prevalence | Background information | Cellulitis – acute | CKS | NICE (opens in a new tab); Causes | Background information | Cellulitis – acute | CKS | NICE (opens in a new tab)

The condition develops when these microorganisms gain entry to the dermis and subcutaneous tissue through breaks in the skin, for example through skin injuries, surgical excisions, intravenous site punctures, fissures between toes, and insect and animal bites. Patients with underlying risk factors are more likely to develop the disease; these include diabetic patients, immunocompromised patients, obesity, advanced age, venous insufficiency and those with chronic renal and liver disease.Sources: Cellulitis – StatPearls – NCBI Bookshelf (opens in a new tab); Risk factors | Background information | Cellulitis – acute | CKS | NICE (opens in a new tab)

Diagnosis

Cellulitis is often diagnosed clinically, with a poorly demarcated area of erythema in the lower limbs that is warm, swollen and tender to touch and can spread rapidly. Constitutional symptoms of fever, malaise and fatigue may be present in moderate to severe cases. Risk factors should be considered which increase the likelihood of cellulitis, along with any recent foreign travel, trauma or injuries to the site that may have allowed the affecting organism to gain entry. The Eron classification system can help categorise the severity of cellulitis, from class 1, where there are no signs of systemic toxicity and the person has no uncontrolled comorbidities, all the way to class 4, where the patient has a life-threatening infection, helping guide management decisions. Bacterial cultures from skin swabs, blood cultures and blood tests are usually reserved for patients who are immunocompromised, have had an animal bite or who have systemic signs and symptoms.Sources: Diagnosis | Diagnosis | Cellulitis – acute | CKS | NICE (opens in a new tab); Diagnosis | Diagnosis | Cellulitis – acute | CKS | NICE (opens in a new tab)

Treatment

The majority of cellulitis infections are mild and can be effectively managed with oral antibiotics effective against streptococcal species. Most commonly this is flucloxacillin; if there is a penicillin allergy, clarithromycin or doxycycline may be prescribed. A marker pen can be used to draw around the extent of the infection to monitor the progress of treatment, with clear safety netting in place to seek immediate medical review if symptoms worsen rapidly. For patients with severe cases that have systemic signs and symptoms, they will typically be managed in hospital and on intravenous antibiotics.Source: Scenario: Management | Management | Cellulitis – acute | CKS | NICE (opens in a new tab)

Folliculitis is a common bacterial infection of the hair follicle, resulting in local inflammation and the formation of pustules or erythematous papules of the overlying hair-covered skin. While the condition usually has a favourable prognosis, prompt recognition can aid in improving the quality of life for the patient and avoid any potential complications.Source: Folliculitis – PubMed (opens in a new tab)

As stated, folliculitis is most commonly caused by a bacterial infection (specifically Staphylococcus aureus) of the superficial or deep hair follicle; however, the condition may also be caused by fungi and viruses, and can even be non-infectious in nature. It is beyond the scope of this patient information context to discuss these individually, but more information regarding the specific causative agents can be found in the source below.Source: Folliculitis – StatPearls – NCBI Bookshelf (opens in a new tab)

Risk factors for developing the condition include patients who are diabetic, immunocompromised and obese. Prolonged use of oral antibiotics can cause folliculitis due to disruptions in the skin’s natural, protective microbiome, allowing resistant bacteria to thrive. Patients who shave a lot are also at risk due to damage to the hair follicle.

Diagnosis

The diagnosis of folliculitis is clinical, with the classical presentation of itchy, red or pus-filled pustules around the hair follicles. The uniformity, location, sensation (itch/pain) and speed of onset can help differentiate between specific causative pathogens. For refractory or severe cases, bacterial or fungal swabs may be sent for microscopy, culture and sensitivity testing, allowing for targeted intervention. Rarely, a skin biopsy may be needed to confirm the diagnosis of certain pathogen causes, specifically in eosinophilic folliculitis. This is a rare cause and usually linked to patients who are immunocompromised.Source: Eosinophilic Pustular Folliculitis – StatPearls – NCBI Bookshelf (opens in a new tab)

Treatment

Many cases of folliculitis do not need medical intervention, as there is often spontaneous resolution within 7–10 days. However, for more severe or persisting cases, these can be effectively managed with often simple interventions. Treatment is dependent on the specific causative agent. For bacterial causes (making up the vast majority of cases), topical antibiotics may be initiated; however, if these are ineffective or a patient presents with deeper folliculitis or extensive involvement of the skin, then oral antibiotics, typically cephalexin or dicloxacillin, will be prescribed for 7–10 days. Maintaining good personal hygiene, using antibacterial soaps and avoiding irritants such as shaving or waxing are all important home relief remedies. For non-bacterial folliculitis, antiviral and antifungal medications can be prescribed depending on the specific underlying pathogen.Source: Folliculitis – StatPearls – NCBI Bookshelf (opens in a new tab)

The herpes simplex virus (HSV) is a common, highly contagious virus, causing lifelong, recurring infections. The virus has two types, type 1 (HSV-1) and type 2 (HSV-2), typically resulting in cold sores or genital herpes, respectively, though HSV-1 is increasingly the cause of genital infections also. The HSV-1 and HSV-2 viruses are highly prevalent, infecting approximately 64% and 13% of the world’s population, respectively.Source: Overview on the management of herpes simplex virus infections: Current therapies and future directions – PubMed (opens in a new tab)

HSV-1 accounts for 90% of all cases of the disease and manifests with painful oral lesions (cold sores) and gingivostomatitis, often preceded by tingling or burning symptoms at the site of infection. HSV-2 typically presents with recurrent, painful genital blisters, ulcers or sores on the genitalia, anus or thighs.Sources: Herpes simplex – oral | Health topics A to Z | CKS | NICE (opens in a new tab); Herpes simplex – genital | Health topics A to Z | CKS | NICE (opens in a new tab)

The virus is spread between individuals through direct skin-to-skin contact of the infected areas. It is most contagious during an outbreak (active sores/blisters) but can be transmitted even when there are no symptoms present. Most forms of the disease are mild and self-limiting, usually within 10–14 days. However, the disease can cause severe, life-threatening complications, including pneumonia and encephalitis (inflammation of the brain); though rare, they typically manifest in patients who are immunocompromised.Source: Herpes simplex – oral | Health topics A to Z | CKS | NICE (opens in a new tab)

Diagnosis

The diagnosis is typically clinical and based on the person’s age and clinical features, such as the history, location and appearance of the lesions. Diagnostic testing can be used to confirm the diagnosis and distinguish between the two types, which can be helpful for prognostic reasons. This is typically a PCR/NAAT swab test, though this is rarely indicated.Source: Herpes Simplex Virus Infections: An Overview of Testing for the Urgent Care Clinician – PMC (opens in a new tab)

Treatment

HSV is a lifelong infection with no cure. Treatment is primarily aimed at managing symptoms, reducing the frequency of outbreaks and lowering the risk of transmission to others. The disease is typically self-limiting in healthy individuals, with a favourable prognosis but with remitting episodes. Ways to avoid the risk of contamination should be explained to the patient, along with practising good hand hygiene and keeping well hydrated, which are all important self-care principles. Treatment with antiviral medications (acyclovir/valacyclovir) can shorten the duration of the outbreak, reduce the severity of symptoms and reduce the risk of complications in immunocompromised/high-risk patients.Source: Acyclovir – StatPearls – NCBI Bookshelf (opens in a new tab)

Tinea corporis, also known as ringworm, is a superficial, highly contagious fungal infection of the body caused by dermatophytes. There are different names for dermatophyte infections that affect various areas of the body: scalp involvement is called tinea capitis, and infections of the face, hands, groin and feet are referred to as tinea faciei, tinea manuum, tinea cruris and tinea pedis, respectively.Source: Tinea Corporis – StatPearls – NCBI Bookshelf (opens in a new tab)

Patients commonly report an itchy, red rash that typically appears on the exposed areas of the neck, trunk or extremities. These present clinically as one or more circular or ovoid lesions, often presenting as patches or plaques. The lesions show sharp margins with a raised, erythematous, scaly edge, sometimes containing vesicles.Source: Tinea Corporis – StatPearls – NCBI Bookshelf (opens in a new tab)

The disease is highly prevalent worldwide, affecting 25% of the general population. Excessive heat and high relative humidity correlate with more frequent and severe disease (due to fungi thriving in warm/damp environments); it is more prevalent in children and young adults but can affect all age groups.Source: Dermatophytes: Update on Clinical Epidemiology and Treatment – PubMed (opens in a new tab)

Diagnosis

The diagnosis is often made clinically, with characteristic lesions. Dermoscopy is a reliable and sensitive diagnostic tool for helping confirm the diagnosis. For atypical presentations, diagnostic tests include skin scraping and a KOH prep, which often gives a rapid diagnosis, or fungal cultures, but these can take up to 4 weeks to give a definitive diagnosis.Sources: Dermoscopic Features seen in Tinea Capitis, Tinea Corporis and Tinea Cruris – PubMed (opens in a new tab); Assessment | Diagnosis | Fungal skin infection – body and groin | CKS | NICE (opens in a new tab)

Treatment

Treatment of dermatophyte infections typically involves the use of topical or oral antifungal agents. The choice between the formulations depends on various factors, such as the severity and extent of the disease, location, patient comorbidities and responses to previous treatments. Topical therapies (clotrimazole, ketoconazole, miconazole, naftifine, terbinafine) applied daily for 2–4 weeks are usually the first-line treatment option for localised infections. Oral therapy is usually reserved for more widespread infections, immunocompromised patients, or those who have failed topical treatments. Oral terbinafine or itraconazole is usually the preferred first-line treatment option, with expected resolution of symptoms within 2–3 weeks. Patients should be given advice on self-care management strategies, including maintaining good personal hygiene by washing affected skin areas daily and drying thoroughly afterwards, and washing clothes and bed linen regularly to eradicate fungal spores and reduce the risk of transmission.Sources: Tinea Corporis – StatPearls – NCBI Bookshelf (opens in a new tab); Scenario: Management | Management | Fungal skin infection – body and groin | CKS | NICE (opens in a new tab)