Cellulitis

What cellulitis is

Bacteria, most often Streptococcus (group A strep) and Staphylococcus aureus, enter through a break in the skin and spread through the dermis and fat. The body's inflammatory response causes redness, heat, swelling and pain. Unlike an abscess, there is no collection of pus, although the two can occur together. Erysipelas is a more superficial form with a raised, sharp edge, often on the face or legs.

Symptoms

• a red, pink, purple or darker area of skin that is spreading. On brown and black skin, redness can be subtle, so warmth, swelling and pain matter more
• swelling and tightness
• warmth to the touch
• pain or tenderness
• blisters in some cases
• fever, chills, tiredness and feeling unwell
• tender, swollen lymph nodes nearby and red streaks (lymphangitis)

Usually only one leg is affected. Redness in both legs is more often something else, such as stasis dermatitis.

Causes and risk factors

• Breaks in the skin: cuts, scrapes, bites, surgical wounds, tattoos, injections
• Athlete's foot: cracks between the toes are a common entry point for leg cellulitis
• Swelling: lymphedema, chronic leg swelling, after lymph node removal
• Skin conditions: eczema, leg ulcers
• Diabetes, obesity, poor circulation
• Previous cellulitis, which damages lymphatics and raises the risk of recurrence
• Injection drug use

Cellulitis of the gums and mouth (dental cellulitis)

Infection from a decayed or cracked tooth, a deep gum pocket in periodontitis, or a partially erupted wisdom tooth can spread from a dental abscess into the soft tissues of the gums, face and neck. This is dental or odontogenic cellulitis. See also cellulitis or abscess of the mouth.

Dental cellulitis symptoms

• a painful tooth, or tender, swollen, red gums around it
• swelling of the cheek, lip, jaw or under the chin, which may be firm and diffuse
• warmth and redness of the facial skin
• difficulty opening the mouth (trismus) or pain on swallowing
• fever, bad taste, bad breath and swollen neck glands
• swelling of the upper lip or around the eye from upper teeth

Why it matters

Mouth infections can spread to the floor of the mouth and neck. Ludwig's angina is a rapidly spreading cellulitis under the tongue and jaw that can block the airway. Upper tooth infections can spread toward the eye. Any facial swelling from a tooth with fever, trouble swallowing or breathing needs emergency care.

Treatment

Antibiotics alone rarely fix dental cellulitis, because the source is the tooth. A dentist or oral surgeon drains the infection by root canal treatment, extraction or incision, and antibiotics such as penicillin or amoxicillin are given while the spread is controlled. Severe cases need hospital IV antibiotics and surgical drainage.

Diagnosis

Cellulitis is diagnosed by examination. Doctors look for the entry point, mark the edge of the redness to track spread, and check for signs of abscess or deeper infection. Blood tests and cultures are used for severe illness. Ultrasound can detect an abscess. Dental X-rays or CT scans locate the source of facial infections. Doctors also consider conditions that mimic cellulitis: deep vein thrombosis, stasis dermatitis, gout, allergic reactions and contact dermatitis.

Treatment

• Oral antibiotics: usually a penicillin or cephalosporin for typical cellulitis, or other agents if MRSA is suspected or there is penicillin allergy. A 5-day course is often enough if improving, extended if not.
• IV antibiotics for severe infection, rapid spread, high fever, facial or eye involvement, or failure of oral treatment.
• Drainage of any abscess.
• Raise the affected limb above heart level to reduce swelling.
• Pain relief: acetaminophen (paracetamol) or ibuprofen. Follow the label dose.
• Treat entry points: antifungal cream for athlete's foot, moisturizer for cracked skin.

Redness can look worse in the first 24 to 48 hours before improving, even with effective antibiotics. Worsening after 72 hours needs review.

Complications

• abscess formation
• bloodstream infection and sepsis
• necrotizing fasciitis, rare but life-threatening
• orbital cellulitis from facial or sinus infection
• recurrent cellulitis and lymphedema

Preventing recurrence

• keep skin moisturized and treat athlete's foot
• clean and cover cuts promptly
• manage leg swelling with compression stockings and leg elevation
• control blood sugar and weight
• keep teeth and gums healthy with regular dental care
• people with frequent recurrences may be offered long-term low-dose antibiotics

Frequently asked questions

What are the first signs of cellulitis?

Early signs are an area of skin that is red or darker than usual, warm, swollen and tender, often near a cut, bite or crack. It spreads over hours to days. Fever, chills and red streaks suggest the infection is spreading and needs prompt treatment.

What are the symptoms of dental cellulitis?

Dental cellulitis causes a painful tooth or gums with spreading swelling of the cheek, jaw or under the chin, warm red skin, fever, bad taste and difficulty opening the mouth or swallowing. Trouble breathing or swallowing saliva is an emergency.

Can you get cellulitis in your gums?

Yes. Infection from a tooth abscess, a deep periodontal pocket or an erupting wisdom tooth can spread into the gums and face as cellulitis. It needs dental treatment to remove the source, plus antibiotics, and urgent care if swelling spreads.

How long does cellulitis take to heal?

Most people improve within 2 to 3 days of starting antibiotics, and redness and swelling clear over 1 to 2 weeks. Skin may peel or stay discolored for a few weeks. Get reviewed if there is no improvement after 72 hours.

Is cellulitis contagious?

Cellulitis itself is generally not passed from person to person, because the infection is in deep skin layers. However, open wounds or draining abscesses can carry bacteria such as MRSA, so cover wounds and wash hands well.