Introduction

Erysipelas and cellulitis are skin infections that can develop if bacteria enter the skin, for instance through a cut or sore. Both infections make your skin swell, become red and tender. Erysipelas (also known as St. Anthony's fire) usually only affects the uppermost layers of skin, while cellulitis typically reaches deeper layers of tissue. Provided the right treatment is started early enough, these infections usually clear up without any lasting effects. Left untreated, they sometimes lead to serious complications.

Despite having a similar name, cellulitis has nothing to do with the more widely known but harmless “cellulite.”

At a glance

• If your skin is broken, for instance through a cut or sore, bacteria can enter it and cause pain, redness and swelling.
• An infection of only the upper layers of skin is called erysipelas.
• If deeper layers are infected, it is called cellulitis.
• Both of these infections are most common on the feet and lower legs.
• They can be treated with antibiotics.

Symptoms

There are two main types of bacterial skin infections:

• Erysipelas
• Cellulitis (deeper infection of the connective tissue)

Both infections are most common on the feet or lower legs, but they may also affect other parts of the body. Erysipelas can develop on the face, and cellulitis may also occur on the palm of the hand, for instance. There it can spread in a V-shape in the tendon sheaths between the thumb, wrist and little finger.

Erysipelas affects the upper layers of the skin. The typical symptom is a painful and shiny light-red swelling of a quite clearly defined area of skin. Red streaks leading from that area may be a sign that the infection has started to spread along the lymph vessels too. In more severe cases, blisters may form as well. Nearby lymph nodes sometimes swell up and become more sensitive to pressure. People usually have a fever and generally feel unwell right from the start of the infection, when the skin first turns red.

Erysipelas: Infection in the upper layers of skin

In cellulitis, the area of reddened skin is less clearly defined than it is in erysipelas, and it is often dark-red or slightly purplish. Unlike erysipelas, the infection caused by cellulitis reaches the lower layers of skin and the tissue beneath it. The infection can spread along tendons and muscles, and pus may form.

Pain and swelling in the infected skin and connective tissue are typical of both forms. Fever and generally feeling ill are more common in erysipelas, but can also occur in severe cellulitis.

Cellulitis: Infection spreads to the subcutis (the deepest layer of skin) or deeper

Causes and risk factors

Erysipelas is often caused by streptococcus bacteria, while cellulitis is typically caused by staphylococcus bacteria. Both types of bacteria may cause either erysipelas or cellulitis, though.

Bacterial skin infections are more likely to arise if the surface of your skin is damaged, making it easier for bacteria to enter. Because of this, the risk factors include skin problems such as eczema, impetigo, fungal infections such as athlete's foot, or wounds and ulcers. Erysipelas or cellulitis can also develop following injuries, pin pricks, and insect or animal bites, or if germs get into the wound during an operation.

The risk of infection is particularly high if you have a weakened immune system. Your immune system may become weaker due to things like taking certain medications. These include some cancer drugs, steroids and medication that is commonly used after organ transplants to suppress the body's immune response.

The risk is also higher in people who are overweight or have diabetes, problems with the circulation of lymph or blood, or have venous insufficiency. Previous erysipelas or cellulitis is considered to be a risk factor too.

Prevalence

Erysipelas and cellulitis are among the most common skin conditions, but it's not known exactly how often they occur. According to some studies, 2 out of 10,000 people are affected each year. Other research suggests that more than 250 out of 10,000 people are affected.

Effects

Untreated bacterial skin infections can cause various complications. These include the following:

• The spread of pus-producing infection and abscesses: Especially in cellulitis, an infection with pus can spread to deeper tissue (such as muscle tissue). Sometimes the pus builds up in natural spaces or gaps between tissue. An abscess is a sealed, pus-filled space that can develop as a result of various bacterial skin infections. It is mostly made up of dead germs, tissue cells, and immune system cells.
• Lymphedema: Parts of the infected lymphatic vessels may be destroyed following an erysipelas infection. This blocks the flow of lymph (the fluid in the lymphatic system), causing it to build up. That results in permanent swelling and poorer circulation in the tissue, increasing the risk of developing further bacterial skin infections.

Life-threatening complications are rare. If bacteria enter the bloodstream, they may cause blood poisoning (septicemia). In rare cases, a bacterial skin infection on the face can cause meningitis (inflammation of the membranes covering the brain and spinal cord) or a blood clot in one of the blood vessels in the brain (cerebral venous thrombosis).

If there are complications, only fast treatment can prevent more serious problems. Signs of a more severe infection include the following:

• Severe pain
• Fever, cold sweats, pale skin
• Nausea
• Faster rate of breathing or a racing heart
• Drowsiness, confusion, or other problems with consciousness or awareness

If you notice any of these symptoms, it is important to call the emergency services immediately.

Diagnosis

Doctors can usually tell whether an infection is erysipelas or cellulitis based on the typical symptoms and the appearance of the skin. Your medical history or recent injuries often help to diagnose the problem too.

Further tests aren't usually needed. It can sometimes help to test fluid from the wound for germs. This is done when doctors think there may be a specific germ causing the infection, for instance because someone’s skin became infected after they were bitten by an animal.

Prevention

People who have had erysipelas or cellulitis are quite likely to develop the same kind of infection again after completing successful treatment. About one third of people who have had an erysipelas infection get it again.

There are various ways to stop this from happening. If a skin condition like athlete’s foot or eczema made it easier for the infection to occur in the first place, it is important to treat that underlying cause first. Also, it's important for people to pay attention to good foot hygiene if they have an increased risk of infection due to diabetes or blood flow problems.

If bacterial skin infections keep occurring, preventive treatment with antibiotics may be considered. When used for this purpose, the antibiotics need to be taken daily over the course of several months.

Treatment

Erysipelas and cellulitis are both treated with antibiotics. The medication is delivered directly into a vein using a drip. In milder cases, tablets are enough. People who go to the hospital for treatment usually have to stay for about a week.

The exact type of antibiotic will depend on several factors, such as what type of bacteria doctors think you have. To check the progress of the treatment, the infected area of skin is outlined with a special pen. This makes it possible to see whether the antibiotics are having an effect and the infection and redness are going away.

It is also recommended that you cool the swelling and apply moist antiseptic wraps. Anti-inflammatory painkillers like ibuprofen can be used to relieve pain and fever.

If the skin on your face is infected, it's better to speak or chew as little as possible. If the skin on a leg or foot is infected, it can help to elevate that leg. Bed rest is even recommended in many cases. People are then given injections to prevent thrombosis.

In more severe cellulitis, surgery may be needed to remove pus and dead tissue.

Further information

When people are ill or need medical advice, they usually go to see their family doctor first. In our topic "Health care in Germany" you can read about how to find the right doctor – and our list of questions can help you to prepare for your visit to the doctor.

Sources

• Dalal A, Eskin-Schwartz M, Mimouni D et al. Interventions for the prevention of recurrent erysipelas and cellulitis. Cochrane Database Syst Rev 2017; (6): CD009758. [PMC free article: PMC6481501] [PubMed: 28631307]
• Kilburn SA, Featherstone P, Higgins B et al. Interventions for cellulitis and erysipelas. Cochrane Database Syst Rev 2010; (6): CD004299. [PMC free article: PMC8693180] [PubMed: 20556757]
• Moll I. Duale Reihe Dermatologie. Stuttgart: Thieme; 2016.
• Oh CC. Cellulitis and erysipelas: prevention. BMJ Clin Evid 2015: pii: 1708.
• Oh CC, Ko HC, Lee HY et al. Antibiotic prophylaxis for preventing recurrent cellulitis: a systematic review and meta-analysis. J Infect 2014; 69(1): 26-34. [PubMed: 24576824]
• Phoenix G, Das S, Joshi M. Diagnosis and management of cellulitis. BMJ 2012; 345: e4955. [PubMed: 22872711]
• Quirke M, Ayoub F, McCabe A et al. Risk factors for nonpurulent leg cellulitis: a systematic review and meta-analysis. Br J Dermatol 2017; 177(2): 382-394. [PubMed: 27864837]
• Stevens DL, Bisno AL, Chambers HF et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis 2014; 59(2): e10-52. [PubMed: 24973422]
• Stevens DL, Bryant AE. Impetigo, Erysipelas and Cellulitis. Oklahoma City (OK): NIH; 2016.

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