Family doctor

Overview

• Boils can range in severity from a pimple to an abscess. They occur when the skin becomes infected by bacteria(usually Staphylococcus aureus).
• Some people are more susceptible than others to boils.
• Single boils may be lanced and heal eventually. Recurrent boils can prove difficult to treat, although there are several possible treatments that may break the cycle including washing with chlorhexidine soap and specialised antibiotic regimens.
• Several methods can be used to treat boils at home, speed up healing and prevent spread to others.
• Anyone with a boil entering a hospital must let medical staff know, to prevent spread of the boil bacteria.

What is a boil?

Boils are a very common skin infection. They are a skin disease and in most cases are not due to anything wrong with the blood.

Another name for a boil is a furuncle, and when multiple boils occur on the body, the condition is called furunculosis.

Several boils joined together with tunnels under the skin are called a carbuncle.

As a boil gets larger it gets a cavity inside it filled with pus. This is called an abscess.

A pimple is a mini-boil.

How are boils formed?

Boils are caused by a hair follicle (a tiny tunnel in the skin where hair grows from) or a tiny cut or scratch becoming infected by a bacteria (usually Staphylococcus aureus).

As a boil starts to develop, the body's immune system carries white cells in the blood to the site of the boil to do battle with the invading bacteria. The body also creates a fibrous wall around the 'battleground" to contain the infection.

Once the boil reaches a certain size, this fibrous wall prevents antibiotics in the bloodstream penetrating into the boil. Dead white cells and dead bacteria make up the liquid pus in the center of the boil and, because this liquid forms under pressure, it becomes painful.

A boil will always start to "point" towards the skin surface and will eventually burst, draining the pus, relieving pain and will then heal. This whole process can take 2 weeks, and often doctors will "lance" the boil early - make a deliberate hole in it to allow the pus to drain - to speed up the healing process.

It is very common for boils to "crop", that is, to occur as several boils that go through their life-cycle and heal and then occur weeks or months later. This condition is known as recurrent staphylococcal furunculosis. This condition can be very distressing and although a blood test will usually be arranged by a doctor(to exclude diabetes and other conditions), it is not often due to anything wrong with the sufferer's internal immunity. It is due to the continuing presence of the bacteria Staphylococcus aureus on the skin and the susceptibility of the person to it.

Who is at risk of getting boils?

Staphylococcus aureus bacteria occurs on the skin of 25% of the average population, with or without the occurrence of boil, but is more prevalent in certain groups.

Usually all sufferers of chronic dermatitis carry Staphylococcus aureus, as do three quarters of those on haemodialysis; half the diabetics taking insulin; and just under half injecting drug users.

What are the treatment options?

If a boil is lanced, a "wick" will usually be inserted. A wick is a piece of ribbon gauze put into the empty cavity of the boil to prevent the hole made in the skin surface closing over too quickly. This allows any further pus that forms to drain through the open hole. The lancing procedure has to be done at the right time. If a boil is lanced too early, there will be no pus to drain and the pain of lancing will have been in vain.

Antibiotics can sometimes prevent a boil forming when used early but will do little to a well developed boil. However antibiotics are sometimes still used to prevent deeper infection occurring.

Staphylococcus aureus bacteria is often resistant to ordinary penicillin so this is not usually prescribed. A special form of Staphylococcus aureus has emerged over recent years called MRSA (Methicillin Resistant Staphylococcus aureus) which can be very difficult to treat with antibiotics and is particularly dangerous when it occurs in hospitals.

How are recurrent cropping boils treated?

Patients suffering recurrent boils need to eradicate Staphylococcus aureus from their skin.

Many types of treatment have been tried to prevent boils cropping without much success. In general, longer continuous courses of antibiotics by mouth do not seem very successful, presumably because they do not act on the Staphylococcus aureus living on the surface of the skin.

Use of a special liquid soap containing chlorhexidine on a long term basis, combined with good hygiene and washing of clothes may help.

The antibiotic mupirocin has been shown to reduce the nasal and hand carriage of Staphylococcus aureus and may prove useful to some sufferers of recurrent boils. A combination of washing using chlorhexidine, and application of mupirocin nasally, twice daily for a week, then three times a week for a further three week period may break the cycle. If this fails, the combination system described below may prove effective.

Various hospitals have developed their own regimens to eradicate carriage of Staphylococcus aureus in nasal passages. To prevent antibiotic resistance, these regimens concentrate on intermittent treatment .(e.g.using two antibiotics, fluctoxacillin and rifampicin.)

This combination is cycled one week in every four (one week on, three weeks off), for a six month period. Flucloxacillin at a dose of 250 mg is taken three times a day on an empty stomach, whilst rifampicin is taken in a single 600 mg morning dose. The patients who have completed this procedure have been successfully stopped recurrent boils, although up to 20% experienced breakthrough occurrences early in treatment. These breakthroughs should be treated conventionally while continuing the regimen.

Those patients allergic to penicillin or with MRSA, substitute fluctoxacillin with clindamycin at a 300 mg dose, three times daily.

Rifampicin causes red discoloration to urine and tears and stains contact lenses; interferes with oral contraceptives; and if used alone, Staphylococcus aureus is almost certain to develop resistance. Rifampicin and clindamycin require specialist approval for use(In New-Zealand).

How can minor boils be treated at home or prevented?

These self-help suggestions may help when a boil occurs.

•   Make sure the boil sufferer uses their own towel and facecloth, and wash these frequently in hot water along with their clothing worn close to the skin.
• Avoid close body contact with other people if a boil is active.
• Eat a good selection of fruit and vegetables and keep good sleep habits.
• Avoid squeezing a boil as it can force infection into the deeper tissues.
• Apply a warm wet compress (towel or other cloth) to the boil for 10 minutes, several times a day to try and speed up its life cycle.

The most simple and practical prevention of boils cropping seems to be once daily use of a special liquid soap containing chlorhexidine on a long term basis, combined with good hygiene and washing of clothes. However some people are sensitive to chlorhexidine and react to it. Boil sufferers visiting or going into hospital for any treatments must let medical staff know they have a boil, to reduce any chance of the Staphylococcus transferring to others in hospital.