Cellulitis is a common but potentially serious bacterial skin infection. Unlike superficial infections, cellulitis affects the deeper layers of the skin and the underlying tissue. If not treated promptly with antibiotics, it can spread to the lymph nodes and bloodstream, becoming life-threatening.
It’s deep: It affects the dermis and subcutaneous tissues.
It’s bacterial: Usually caused by Staphylococcus or Streptococcus.
It’s not contagious: You cannot catch cellulitis from another person.
It requires antibiotics: It will rarely clear up on its own.
It can look like a blood clot: It is often confused with DVT (Deep Vein Thrombosis).
Cellulitis most commonly appears on the lower legs, but it can occur anywhere on the body, including the face.
The “Signature” Signs:
Expanding Redness: A patch of red skin that gets larger over hours or days.
Swelling and Warmth: The area feels significantly hotter than the surrounding skin.
Pain and Tenderness: The area is often very sore to the touch.
Skin Changes: The skin may look pitted (like an orange peel) or develop blisters.
Cellulitis can progress into Sepsis (blood poisoning). Seek immediate medical attention or call 999 if you have the skin symptoms above plus:
A very high temperature or feeling hot and shivery.
A fast heartbeat or rapid breathing.
Purple patches: Or a “tracking” red line leading away from the infection site.
Confusion or disorientation.
The infection happens when bacteria enter the skin through a break. Even a microscopic crack is enough.
How Bacteria Enter:
Skin injuries: Cuts, insect bites, or surgical wounds.
Skin conditions: Eczema, athlete’s foot (cracks between toes), or psoriasis.
Chronic swelling: Lymphoedema or long-term leg swelling.
Who Is at Higher Risk?
While anyone can get it, you are at a higher risk if you have diabetes, a weakened immune system, or poor circulation. In the elderly, cellulitis can be particularly aggressive and requires early intervention.
Doctors usually diagnose cellulitis by looking at the skin.
Clinical Tip: Doctors often draw a circle around the edge of the redness with a pen. If the redness spreads outside the circle after starting antibiotics, it tells the doctor the treatment may need to be adjusted.
Differential Diagnosis (What else could it be?)
It is vital to rule out:
DVT (Blood Clot): Usually causes swelling and pain but less redness/heat than cellulitis.
Erysipelas: A more superficial infection with very sharp, raised borders.
Dermatitis: Often itchy rather than painful.
Antibiotics are the “gold standard” for treating cellulitis.
Mild/Moderate Cases: Oral antibiotics (usually Flucloxacillin or Clarithromycin) taken for 5 to 7 days.
Severe Cases: If you have a high fever or the infection is spreading rapidly, you may need Intravenous (IV) antibiotics in a hospital setting.
How to Help Yourself at Home:
Elevate: Keep the affected limb higher than your heart to reduce swelling.
Hydrate: Drink plenty of water.
Pain Relief: Use Paracetamol or Ibuprofen as directed.
If ignored, the infection can lead to:
Abscess: A collection of pus that may need surgical draining.
Sepsis: A systemic inflammatory response that can lead to organ failure.
Necrotising Fasciitis: A rare “flesh-eating” infection (an extreme emergency).
If you have had cellulitis once, you are more likely to get it again.
Moisturise: Keep skin hydrated to prevent cracks.
Treat Athlete’s Foot: Fungal infections between toes are a common “gateway” for bacteria.
Wound Care: Clean even minor cuts with antiseptic and cover them.
Manage Swelling: If you have lymphoedema, wear your compression stockings as prescribed.
Cellulitis is a deep-skin infection that starts with redness and heat. Because of the risk of sepsis, you should always consult a GP or visit an Urgent Care Centre if you suspect you have it. With the right antibiotics, most people see improvement within 48 hours.
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