A unique child: Health - A doctor's diary ... Impetigo

By and large, impetigo is a common and benign bacterial skin infection that affects children. Parents usually worry about it because of its unsightliness and perhaps more importantly, its potential for spread. Around 3 per cent of one- to four-year-olds will have an episode of impetigo in any given year in the UK. Infections tend to occur more frequently in the summer months when the skin often is not covered with clothing.

CAUSES

Impetigo is most commonly caused by either group A streptococci, Staphylococcus Aureus, or indeed a mixture of the two. Group A streptococci are responsible for bacterial tonsillitis and can cause many other infections including pneumonia. Staphylococcus Aureus is commonly responsible for cellulitis, another type of skin infection.

RISK FACTORS

A breech in the natural defences of the skin, usually by a small cut, insect bite or even a scratch, allows the bacteria which otherwise lie innocuously on the skin surface to take hold. It takes four to ten days from when the bacteria have entered a breach in the skin, before impetigo manifests itself.

Bacteria from somebody who already has impetigo may be transferred easily from one person to another. In fact, impetigo is so contagious that bacteria may be transferred by sharing towels or even toys.

Children may be more likely to develop impetigo by virtue of playing in close proximity to each other in nursery or school, combined with poor adherence to hygiene measures.

Some children, however, will be more prone to developing impetigo than others. Skin conditions like eczema, headlice or scabies predispose to what is known as secondary impetigo. While most who develop impetigo will have a healthy immune system, those particularly at risk are children with defective immune systems caused by primary immunodeficiency, drugs, or conditions such as diabetes, HIV and leukaemia. In these children, the impetigo will be more aggressive and more difficult to treat and they will be more prone to complications.

PRESENTATION

The classic presentation of impetigo is a well-circumscribed painless red lesion, usually around the nose or mouth. The lesions, which may be itchy, quickly develop a honeycomb-like yellow crust. They usually heal without scarring.

COMPLICATIONS

Unusually, some patients develop bullous impetigo, which more commonly occurs on the trunk. In this type, blisters occur prior to the development of the honeycomb crusts.

In some children, impetigo provides a gateway for bacteria to enter the deeper layers of the skin causing pain, redness and fever. This is known as cellulitis and while usually benign, it may be serious and even cause blood poisoning, known as septicaemia. Local lymph nodes may enlarge and the lymphatic vessels may become infected, which is known as lymphangitis.

Scarlet fever and an inflammatory condition of the kidneys, known as glomerulonephritis, may complicate impetigo on rare occasions. Guttate psoriasis, which may complicate streptococcal infections, causes small scaly lesions, particularly on the trunk.

TREATMENT

For most children, impetigo resolves without treatment by virtue of the body's own defences. Patients often present to their doctor because of complications or concern about spreading the infection. In the absence of complications, impetigo may be treated with an antibiotic cream such as fucidic acid. In patients with other health problems or rapidly spreading impetigo, or if there are complications, children will require antibiotics by mouth or even intravenously.

The impetigo ceases to be infective two days after treatment has commenced. Despite treatment, measures need to be taken to reduce the risk of spread. These include:

• - regular and thorough handwashing
• - avoiding touching the lesions
• - not sharing towels or flannels
• - cleaning toys
• - keeping children at home until the impetigo stops weeping, or 48 hours after antibiotics have been started, in order to prevent spread among the nursery community.

In essence, impetigo is a common and usually easily treatable condition. While complications may occur, they are unusual. The primary issue is to ensure spread of this highly contagious condition is contained.