What is impetigo?

Impetigo is a superficial cutaneous infection that impacts the outer layer of the skin. It is highly contagious and tends to be more common among young children. However, it can be seen in people of all ages.^3,5 

What are the causes of impetigo?

Impetigo is caused by the bacteria Staphylococcus aureus and Streptococcus pyogenes.^1,2 Non-bullous impetigo is attributed to Staphylococcus aureus in 75-80% of cases, Staphylococcus pyogenes in 10% of cases, and a combination of both organisms in 10% of cases. Similarly, bullous impetigo is primarily caused by the bacteria Staphylococcus aureus. This form of impetigo has the potential to impact undamaged skin. However, 

methicillin-resistant Staphylococcus aureus (MRSA) is becoming a more common cause of impetigo linked to its non-bullous form.

In regions with higher temperatures, Streptococcus pyogenes tend to be more abundant. These and other impetigo-causing bacteria get passed from one person to another through touching the skin directly or sharing bedding, clothes, and towels. They typically exploit compromised skin from injuries such as cuts or insect bites, as well as conditions like head lice, scabies, cold sores, or eczema. However, impetigo can also impact skin that is healthy.

How does impetigo manifest?

There are two forms of impetigo: non-bullous impetigo, which is the most prevalent type, and bullous impetigo.

• Non-bullous Impetigo: Its symptoms include red, itchy spots popping up around the nose and mouth. These spots develop into thick, golden crusts about 2cm in size before eventually drying up. Once the crusts fall off, red marks can be left behind. However, these typically go away after 2-3 weeks without leaving a scar. Rarer symptoms include a fever and swollen glands⁴
• Bullous Impetigo: This is a relatively uncommon skin infection that predominantly affects infants. The infection includes the formation of large, fluid-filled blisters of 1 to 2cm in size that usually appear on the central part of the body. These blisters can hurt but there's no redness on the skin around them. The blisters turn clear and soft, then pop and form crusts. Their crusts usually heal up without leaving any scars. Symptoms like fever and swollen glands are common in bullous impetigo²

If left untreated, impetigo can progress into a more serious infection called ecthyma (a deep tissue impetigo-like infection). Ecthyma develops deeper in the skin and can cause painful blisters that develop into open wounds. These eventually form thick crusts with redness around them that often heal forming scars.

 What are the risk factors for impetigo?

• Inadequate hygiene practices
• Increased temperatures and humidity
• Overcrowded and socioeconomically disadvantaged living conditions
• Coexisting conditions that weaken the immune system, such as diabetes and malnutrition
• Exposure to individuals with impetigo
• Factors that may result in skin breaks, including cuts, burns, insect bites, eczema, or contact dermatitis^2,6

What are the potential complications associated with impetigo?

On rare occasions, complications may arise, such as post-streptococcal glomerulonephritis (a kidney disorder) and rheumatic fever ( a condition that impacts the heart, joints, brain and skin).⁶

How is impetigo diagnosed?

The healthcare providers will assess and diagnose impetigo by evaluating the appearance of the lesions. A precise diagnosis can be achieved by obtaining a tissue or fluid sample from the lesion for a laboratory culture, which can identify the specific pathogen responsible for the illness. This diagnostic test will also assist the physician in determining the most appropriate antibiotic treatment.^1,2

Differential diagnosis of impetigo

Bacterial skin infections like:

• Cellulitis - an acute bacterial infection characterised by pain, swelling, erythema and warmth⁷
• Necrotising fasciitis - a rare and potentially life-threatening infection that may occur in the event of wound contamination⁸
• Staphylococcal scalded skin syndrome - a rare, superficial blistering skin condition, characterised by widespread erythema and exfoliation, primarily occurring in children under the age of five⁹
• Erysipelas - a superficial skin infection, less serious than cellulitis that often affects the face¹⁰

Parasitic infestations like scabies (an itchy rash caused by mites).

Fungal skin infections such as:

• Candidiasis - a fungal infection resulting from an excessive proliferation of yeast within the body. Antifungal medications are used to treat candidiasis and can effectively resolve the infection in a period ranging from two days to two weeks, depending on the severity of the condition¹¹
• Tinea corporis (ringworm) - a superficial fungal infection of the skin caused by dermatophytes, affecting various regions of the body such as the trunk, neck, arms, and legs. This condition is prevalent globally¹²
• Tinea capitis - a fungal infection of the scalp, known as 'tinea capitis' or 'scalp ringworm', denotes an infection of the scalp hair follicles and surrounding skin that is triggered by dermatophytes¹³

Non-infective skin conditions like:

• Atopic or contact dermatitis - a skin inflammation caused by contact with irritants leading to rashes, dryness, and itchiness¹⁴
• Eczema
• Burns
• Scalds

What is the treatment of impetigo?

As impetigo is caused by a bacterial infection, the recommended course of treatment includes the administration of antibiotics. Depending on the severity and extent of the condition, doctors may recommend topical antibiotics to be applied directly to the affected skin areas or oral antibiotics for widespread impetigo affecting multiple areas of the body. Scarring is uncommon.^1,3,4

The antibiotic cream is typically applied 3 to 4 times daily for a duration of 7 days. Prior to applying the cream, it is recommended to cleanse any affected skin areas with warm, soapy water and remove any crusts that may have formed. In order to minimise the potential spread of the infection, it is crucial to wash hands promptly before and after applying the cream or, alternatively, utilise latex gloves during its application.

Antibiotic tablets may be recommended in cases where the infection is more severe and widespread. Typically, these medications must be taken 2 to 4 times daily for a duration of 7 days.

How to prevent impetigo?

• Maintain hand hygiene by ensuring your hands are kept clean. It is recommended to wash your hands consistently. If soap and water are not available, utilise an alcohol-based sanitiser
•  Refrain from scratching cuts or wounds
• Clean wounds by washing cuts, scrapes, and injuries with soap and water. This should be followed by the application of an antibiotic cream or ointment onto the wound. After cleaning, it is advised to cover draining or open wounds with clean and dry bandages until they have fully healed
• Ensure linens remain clean by washing underwear, towels, and sheets in hot water
• To prevent further complications from wounds and infections, individuals should refrain from immersing themselves in hot tubs, natural bodies of water (such as lakes, rivers, and oceans), and swimming pools

Summary

Impetigo is a highly contagious skin condition, that has the potential to impact individuals of all racial backgrounds. Most commonly affecting kids between 2 and 5 years, it can also be present in older children and adults. Individuals with diabetes or weakened immune systems are at a higher risk of developing impetigo.

Impetigo is primarily characterised by red, sore and itchy skin, most common on the face (around the nose and mouth) and hands. It is caused by bacteria which spread via direct contact with infected skin or open wounds. It can be contagious for weeks until the rash disappears and scabs fall off.

Impetigo diagnosis is usually based on the symptoms and clinical manifestations. Treatment involves topical and oral antibiotics. With treatment, impetigo typically clears up in just a few days. However, without treatment, the infection takes between 1 and 3 weeks to heal. Scarring is uncommon after healing, although there may occur pigmentation changes in certain individuals.