Cellulitis

Overview

Cellulitis makes the skin painful, hot and swollen, and the area usually looks red, though this may be less obvious on brown or black skin. It can occur on any part of the body, but it is more common on the lower limbs. Bacteria get into the deeper layers of the skin through a break in the skin, such as an insect bite or cut. If it is not treated quickly, the infection can spread to other parts of the body, such as the blood, muscles and bones. Cellulitis is treated with antibiotics.

Symptoms

What a clinician may find

• Skin that is painful, hot, swollen and usually red.
• Redness that may be less obvious on brown or black skin.
• Flu-like symptoms, including feeling unwell.

Complications

• Spread of the infection to the blood, muscles and bones if it is not treated quickly.
• Sepsis (blood poisoning), when bacteria spread from the cellulitis to the bloodstream.
• Abscesses, which are collections of pus that may need draining.
• Lymphoedema, because cellulitis can damage the lymphatic system.
• Necrotising fasciitis, a severe and rapidly spreading infection of the muscle and connective tissue.

Diagnosis

Cellulitis is mainly diagnosed clinically, by a clinician examining the affected area and looking for spreading red inflammation of the deeper skin. A skin swab or blood tests may be taken, although identifying the bacteria is rarely possible. Because the symptoms are similar to those of a blood clot, a doctor may ask for further tests to rule out a deep vein thrombosis.

Treatment

Mild cellulitis affecting a small area of skin is usually treated with antibiotic tablets, usually for about a week. NICE advises oral antibiotics first when the person can take tablets and the condition does not need antibiotics given into a vein. Severe cellulitis may need hospital treatment. NHS Inform describes paracetamol or ibuprofen for pain, and raising the affected area when sitting or lying down.

Prevention

People at higher risk can help prevent cellulitis by treating skin problems such as eczema and athlete's foot, and by keeping weight at a healthy level. NICE advises against routine antibiotics to prevent cellulitis coming back, although people who keep getting it may be prescribed long-term antibiotics.

Key facts

What are the symptoms of cellulitis?

Cellulitis makes the skin painful, hot and swollen. The area usually looks red, but this may be less obvious on brown or black skin. It can occur on any part of the body, but it is more common on the lower limbs, and less commonly affects the arms or torso. Some people also feel unwell with flu-like symptoms, and may have swollen, painful glands. The skin may blister.

NHS 111 Wales also describes red streaks spreading from the affected area. Symptoms may get worse in the first 48 hours of treatment before they start to improve. Changes in skin colour can persist after cellulitis, and are more common if it has affected the same area more than once. Cellulitis is not passed from person to person, because it affects the deeper layers of the skin.

Cellulitis in the eye is very serious. The route to care for cellulitis near the eye is described in the last section of this article.

What causes cellulitis and who is more likely to get it?

Cellulitis is an infection caused by bacteria getting into the deeper layers of the skin. A break in the skin, such as an insect bite, a cut or cracked, dry skin, lets the bacteria into the deeper tissues. The bacteria most often involved are streptococci and Staphylococcus aureus.

The NHS lists poor circulation, a weakened immune system, lymphoedema, injecting drugs, a wound from surgery and having had cellulitis before as risk factors. A weakened immune system can be due to chemotherapy or diabetes. NHS Inform adds that being overweight can increase the chance of developing cellulitis or slow recovery from it. Skin conditions such as eczema, or a fungal infection of the feet called athlete's foot, can break the skin and make it easier for bacteria to enter. The British Association of Dermatologists lists lymphoedema both as a risk factor and as a complication. Once someone has had cellulitis, it is more likely to return in the same part of the body.

How is cellulitis diagnosed?

Cellulitis is mainly diagnosed clinically, by a clinician looking at the affected area. Diagnosis is usually made from the clinical picture, based on spreading red inflammation of the deeper skin. A skin swab or blood tests may be taken, although identifying the bacteria is rarely possible. NICE notes that in most cases swabbing of cellulitis gives negative results, especially when the skin is intact.

A UK hospital leaflet says that because the symptoms are similar to those of a blood clot, a doctor may ask for further tests to rule out a deep vein thrombosis. Other skin conditions, such as venous stasis dermatitis and contact dermatitis, can look like cellulitis. Erysipelas is a related infection that affects the upper layers of the skin, while cellulitis reaches deeper tissue. The two can overlap, so a definite diagnosis is not always possible. Cellulitis tends to have ill-defined borders and develop more slowly, while erysipelas has better-defined borders and develops faster.

How is cellulitis treated?

Mild cellulitis affecting a small area of skin is usually treated with antibiotic tablets, usually for about a week. NICE advises oral antibiotics first when the person can take tablets and the condition is not severe enough to need antibiotics given into a vein. If antibiotics are given into a vein, NICE advises a review by 48 hours and a switch to tablets if possible. For infection near the eyes or nose, NICE suggests a different first-choice antibiotic and says specialist advice may be sought.

If cellulitis is severe, the person might need hospital treatment with antibiotics given into a vein. NHS Inform describes paracetamol or ibuprofen for pain, and raising the affected area on a chair or pillow when sitting or lying down. NHS Inform also says that stopping antibiotics early can cause cellulitis to come back. Symptoms may get worse in the first 48 hours of treatment before they begin to improve. NICE advises seeking medical help if symptoms worsen rapidly or significantly at any time, or do not start to improve within 2 to 3 days.

Can cellulitis cause complications or come back?

Most people make a full recovery with no long-lasting effects. If cellulitis is not treated quickly, the infection can spread to other parts of the body, such as the blood, muscles and bones. Infection that spreads to the blood can cause blood poisoning, also called septicaemia or sepsis. In severe cases an abscess, a collection of pus, can form and may need draining. Necrotising fasciitis is a severe and rapidly spreading infection of the muscle and connective tissue. Cellulitis can also damage the lymphatic system, which can cause permanent swelling of the affected arm or leg.

Cellulitis can come back. The British Association of Dermatologists notes that it is more likely to return in the same part of the body, and that fixing skin breaks such as athlete's foot or eczema can help. NICE advises that antibiotics should not be offered routinely to prevent it coming back. NHS Inform says people who keep getting cellulitis may be prescribed long-term antibiotics, and may be referred to a dermatologist, a skin specialist.

When should you get medical help for cellulitis?

The NHS advises an urgent GP appointment or NHS 111 for skin that is painful, hot and swollen. NHS 111 Wales lists rapidly spreading redness among the signs for which urgent help through NHS 111 is advised.

The NHS advises calling 999 or going to A&E for signs of serious complications. It lists a very high temperature, feeling hot, cold or shivery, a fast heartbeat or breathing, purple patches on the skin, dizziness or fainting, confusion, cold clammy or pale skin, and loss of consciousness. It advises against driving to A&E in this situation; someone else can drive, or 999 can be called for an ambulance.

Cellulitis in the eye is very serious. Cellulitis near the eyes or nose can need specialist advice, and urgent assessment through NHS 111 or a same-day GP appointment is the usual route, with 999 or A&E for the emergency signs above. NICE advises seeking medical help if symptoms worsen rapidly or significantly at any time, or do not start to improve within 2 to 3 days of starting antibiotics.

Frequently asked questions