Cellulitis
Also known as Skin infection
This article is general health information for the selected condition. It is not a diagnosis and does not replace clinical judgement. If you have questions or need treatment advice, please consult a qualified healthcare professional.
What is cellulitis?
Cellulitis is a bacterial infection of the deeper skin and underlying tissue, most often on the lower leg. It causes a spreading area of redness, warmth, swelling and tenderness, usually on one side only. It requires antibiotics and can progress quickly, so marking the edge of the redness helps track whether treatment is working.
Causes
- Streptococcus bacteria, the most frequent cause
- Staphylococcus aureus including resistant strains
- Entry through a cut, bite, ulcer or cracked skin
- Athlete foot creating skin breaks between the toes
Symptoms
- Spreading redness that is warm and tender
- Swelling of the affected area
- Pain
- Fever and chills
- Skin that may look tight or shiny
- Blistering in more severe cases
- Swollen nearby lymph nodes
Risk factors
- Skin breaks, wounds or ulcers
- Lymphoedema or chronic leg swelling
- Diabetes
- Obesity
- Previous episode of cellulitis
- Weakened immune system
Diagnosis
- Clinical assessment of the affected skin
- Marking the border of redness to monitor spread
- Blood tests including inflammatory markers when systemically unwell
- Blood cultures if fever is present
- Ultrasound to exclude abscess or clot when uncertain
Treatment
- Oral antibiotics for most uncomplicated cases
- Intravenous antibiotics when severe or rapidly spreading
- Elevation of the affected limb
- Analgesia
- Treating the entry point such as athlete foot
- Urgent surgical review if necrotising infection is suspected
Self care
- Take the full antibiotic course even once redness improves
- Draw around the edge of the redness to track whether it is spreading
- Elevate the affected limb as much as possible
- Take paracetamol or ibuprofen for pain
- Keep the skin clean and moisturised once healing
- Treat athlete foot, a common entry point
- Wear compression stockings if advised for chronic swelling
When to see a doctor
Book an appointment if:
- Redness spreading despite 48 hours of antibiotics
- Fever not settling
- Recurrent episodes in the same limb
- Underlying leg swelling or ulceration
- Diabetes with any foot skin infection
- Blistering or skin breakdown
Some symptoms need emergency care rather than an appointment. See the warning signs listed above.
Prevention
- Treat athlete foot and any skin cracks promptly
- Moisturise dry skin to prevent breaks
- Manage leg swelling and lymphoedema with compression
- Clean and cover cuts and bites
- Control diabetes and check feet daily
- Consider preventive antibiotics after repeated episodes
Outlook
Most uncomplicated cellulitis responds to oral antibiotics within a few days, though redness can take a week or two to fade fully. Recurrence is common where leg swelling, lymphoedema or athlete foot persist, so treating those matters as much as the antibiotic. Necrotising infection is rare but rapidly life threatening, which is why disproportionate pain is taken seriously.
Common questions
Can cellulitis affect both legs at once?
Rarely. Redness affecting both legs symmetrically is more often venous eczema or chronic swelling. Genuine cellulitis is usually one sided, which is a useful distinguishing feature.
When should I seek urgent care?
Rapid spread, severe pain out of proportion to the appearance, dusky or blackened skin, high fever or confusion can indicate a deeper or necrotising infection and need emergency assessment.
Why does cellulitis keep coming back?
Recurrence is common when the underlying cause persists, such as chronic leg swelling, lymphoedema or untreated athlete foot. Addressing these, along with skin care and compression where appropriate, reduces repeat episodes.
References
Important: Dard AI is not a medical device and does not diagnose, treat, or replace clinician judgement. This article is general information only. Always consult a qualified healthcare professional about diagnosis and treatment, and seek emergency care for severe or rapidly worsening symptoms.