Cellulitis

Cellulitis is a bacterial infection of the skin and underlying flesh. Symptoms include redness and swelling, often accompanied by a general feeling of being unwell. The face, neck, arms and legs are the areas most commonly affected. Treatment is with antibiotics.

Causes

Cellulitis is usually caused by bacteria that may be present on your skin, or in external sources such as water, soil or animals that you come in contact with. Cellulitis is often, but not always, preceded by a skin problem such as a scrape, cut, puncture wound, bee or wasp sting, ulceration, or surgical wound; or another skin condition such as eczema, psoriasis, athlete's foot or scabies. Other factors than can increase the chances of developing cellulitis include:

• Problems with circulation in the limbs
• Diabetes
• Alcoholism
• Obesity
• Swelling of the legs
• Pregnancy
• Weakened immune system , eg: HIV/AIDS
• Previous cellulitis.

A variation of the condition, called orbital cellulitis, affects the tissues around the eye. This form of cellulitis can be caused by bacteria that have spread from the nose, throat or sinuses.

Signs and symptoms

The onset of cellulitis is often sudden. A clearly defined area of skin becomes red and tender. It rapidly turns bright red, shiny, swollen and feels hot. The affected area may keep growing in size and be painful to touch.

During the initial stages of the rash there is often accompanying fever, chills, headache, nausea and a general feeling of being unwell. Lymph nodes near the affected area may become swollen and tender.

Cellulitis is a serious infection. A doctor should be seen if the affected area is larger than a 10 cent coin. If the cellulitis is near an eye, very painful, or growing rapidly, see a doctor urgently.

Diagnosis

Cellulitis can usually be diagnosed from its characteristic appearance. Blood tests and tissue cultures may be used to confirm the presence of bacterial infection. In cases of orbital cellulitis, a CT scan (computerised tomography) may be recommended in order to precisely identify the extent of the infection.

Treatment

It is important to seek prompt medical advice if cellulitis is suspected so that an accurate diagnosis can be made and effective treatment given. The condition is treated with antibiotics, usually penicillin-based. In most cases treatment with oral antibiotics is all that will be required to adequately treat the condition. Oral antibiotics are usually given for 5–10 days. In many cases improvement in symptoms occurs within 48 hours of starting treatment.

In cases where the cellulitis is severe, or where oral antibiotics do not prove effective, hospitalisation and treatment with intravenous antibiotics may be required.

If orbital cellulitis is suspected, assessment and treatment from an eye specialist (ophthalmologist) may be required as the potential complications of the condition include loss of vision and meningitis.

In all cases elevation of the affected area (where possible) and bed rest is important. Measures such as cold packs and pain relieving medication may be used to reduce pain and discomfort.

In rare cases:

• The bacteria that caused the cellulitis can spread to the bloodstream and travel throughout the body. This is known as sepsis which can be life-threatening, and will require urgent hospital treatment.
• The infection can spread to the deep layer of tissue known as the fascial lining. Necrotizing cellulitis and necrotizing fasciitis are severe forms of cellulitis that require immediate medical attention.

It is possible for cellulitis to recur. This is particularly true of patients who have an underlying medical condition such as diabetes, postphlebitic syndrome or HIV infection. In selected patients where recurrence is a serious problem, on-going preventative treatment with antibiotics may be recommended.

Prevention

Good skin care can help to prevent cellulitis:

• Inspect your feet daily for signs of injury or infection
• Wash and dry hands properly
• Moisturise your skin regularly, to help prevent cracking and peeling
• Trim your fingernails and toenails carefully, taking care not to injure the surrounding skin
• Avoid sharing towels and bed linen
• Wash linen, towels and clothing regularly
• Wear appropriate footwear and gloves to protect feet and hands
• Treat skin infections early, eg: athlete's foot.

Children with cellulitis should avoid school or pre-school until the affected area has dried up, or for at least one day after oral antibiotic treatment has been started.

References

Leversha, A. and Naylor, D. (2019). Cellulitis (Web Page). Starship Clinical Guidelines. Auckland: Starship Child Health. https://www.starship.org.nz/guidelines/cellulitis [Accessed: 31/01/20]
Mayo Clinic (2015). Cellulitis (Web Page). Rochester, MN: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/cellulitis/symptoms-causes/syc-20370762 [Accessed: 31/01/20]
Ministry of Health (2018). Cellulitis (Web Page). Wellington: New Zealand Government Ministry of Health. https://www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/cellulitis [Accessed: 31/01/20]
Stanway, A. (2016). Cellulitis (Web Page). Hamilton: DermNet New Zealand. https://www.dermnetnz.org/topics/cellulitis/ [Accessed: 31/01/20]
O’Toole, M.T. (Ed.) (2017). Cellulitis. Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MI: Elsevier.

Last Reviewed – February 2020

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