Cellulitis (skin infection)
Created: 09.01.2025
Updated 20.04.2026
Approved by: Consultant Dermatologist, Dr James Denny
What is Cellulitis?
Cellulitis is a common bacterial infection of the skin that affects the deeper layers of the dermis and the underlying soft tissues. It develops when bacteria enter through a break in the skin barrier.
The most common bacteria responsible are Streptococcus and Staphylococcus aureus, which are part of the normal skin flora but can cause infection if they penetrate deeper tissues.
Cellulitis affects people of all ages and can occur anywhere on the body. It is most frequently seen on the lower legs, but the arms, face, and around the eyes may also be involved.
Even minor skin injuries such as a small cut, cracked skin, surgical wound, or an insect bite can provide an entry point for infection.
Who is at risk of developing cellulitis?
Certain individuals have a higher risk of developing cellulitis. Recognising these risk factors is important for prevention.
Common risk factors include:
- Eczema, athlete’s foot, or other inflammatory skin conditions
- Chronic leg swelling or lymphoedema
- Diabetes
- Obesity
- Poor circulation
- Weakened immune system
- Previous episodes of cellulitis
People with chronic swelling of the legs are particularly prone to recurrent cellulitis, as impaired lymphatic drainage reduces the body's ability to fight infection locally.
What are the symptoms?
Symptoms typically develop quickly and may worsen over hours or days.
Common features include:
- Redness that spreads
- Pain or tenderness
- Warmth over the area
- Swollen skin that feels tight or stretched
- Shiny appearance of the affected skin
In mild cellulitis, symptoms may be limited to local redness and discomfort. In more advanced cases, patients may develop:
- Fever and chills
- Fatigue
- Swollen lymph nodes
- General feeling of being unwell
The borders of the redness are usually not sharply defined, and the area may expand if untreated.
If left untreated, cellulitis can lead to complications such as abscess formation, deeper tissue infection, or spread of bacteria into the bloodstream.
How is cellulitis diagnosed?
Cellulitis is usually diagnosed clinically by a healthcare professional based on the appearance of the skin and the patient’s symptoms.
Blood tests or imaging are not routinely required but may be used in severe cases or when complications are suspected. Early diagnosis is essential to prevent progression.
Specialist dermatology assessment may be helpful when the diagnosis is uncertain, particularly to distinguish cellulitis from other conditions such as deep vein thrombosis, contact dermatitis, or inflammatory skin disorders that can mimic infection.
What are the treatments?
Prompt antibiotic treatment is essential.
Mild cellulitis
Most cases of mild cellulitis can be treated with oral antibiotics at home. Symptoms typically begin to improve within 48 to 72 hours of starting treatment.
More severe infection
If symptoms are extensive, worsening rapidly, or associated with systemic illness, hospital admission for intravenous antibiotics may be required.
Supportive measures include:
- Elevating the affected limb
- Rest
- Adequate hydration
- Pain relief where needed
Completing the full course of antibiotics is crucial, even if symptoms improve early.
Recurrent cellulitis
Some patients experience recurrent cellulitis, particularly if underlying risk factors are not addressed.
Management may include:
- Treating chronic skin conditions
- Managing swelling or lymphoedema
- Preventative long-term antibiotics in selected cases
- Optimising diabetes control
Specialist dermatology and medical review can help reduce recurrence and identify contributing factors.
How can you prevent cellulitis?
Steps to prevent cellulitis focus on maintaining skin integrity and reducing risk factors.
Preventative measures include:
- Prompt cleaning and covering of cuts or wounds
- Treating fungal infections such as athlete’s foot
- Regular moisturising to prevent cracked skin
- Managing chronic swelling
- Wearing protective clothing to reduce injury risk
Patients with a history of cellulitis should seek early medical advice if signs of infection reappear.
What is the prognosis?
With early diagnosis and appropriate antibiotic treatment, the prognosis for cellulitis is generally excellent. Most people recover fully without long-term complications.
However, delayed treatment increases the risk of serious outcomes, including bloodstream infection or chronic swelling due to lymphatic damage.
Individuals with underlying health conditions may require closer monitoring to prevent recurrence and complications.
Frequently Asked Questions
How do I know if I am developing cellulitis?
Early signs include spreading redness, warmth, pain, and swollen skin in one area, often on the leg. The skin may feel tight and tender. Fever or feeling unwell can develop as the infection progresses. Prompt medical assessment is important if these symptoms appear.
Can cellulitis start from something minor like an insect bite?
Yes. Even a small break in the skin, such as an insect bite, cut, cracked skin, or scratch, can allow common bacteria to enter and cause infection. Keeping wounds clean and covered reduces the risk.
How long does cellulitis take to improve with antibiotic treatment?
With appropriate antibiotic treatment, mild cellulitis often begins to improve within 48 to 72 hours. However, the full course of antibiotics must be completed to ensure the infection clears completely.
Why does cellulitis sometimes come back?
Recurrent cellulitis is more likely in people with ongoing risk factors such as chronic swelling, eczema, athlete’s foot, diabetes, or previous episodes of infection. Managing these underlying conditions helps reduce recurrence.
When should cellulitis be treated urgently?
Immediate medical attention is needed if redness spreads rapidly, pain becomes severe, fever develops, or you feel generally unwell. These may indicate a more serious infection requiring urgent care.
