What information and treatment should I receive for possible cellulitis of the ankle?

Information for Possible Ankle Cellulitis

If you have redness, warmth, swelling, and tenderness around your ankle that is spreading, you likely have cellulitis—a bacterial skin infection that requires antibiotic treatment for 5 days if improvement occurs.

What Cellulitis Is and What Causes It

• Cellulitis is an infection of the deep skin layers and tissue beneath the skin, presenting as expanding redness, warmth, swelling, and pain 1.
• The infection is caused by bacteria—most commonly beta-hemolytic streptococci (especially Streptococcus pyogenes) in approximately 85% of cases, with methicillin-sensitive Staphylococcus aureus accounting for most remaining cases 1, 2.
• In the majority of cellulitis cases (approximately 85%), no bacteria can be cultured from the infection site, so diagnosis relies entirely on clinical appearance rather than laboratory tests 2, 3.

How to Recognize Cellulitis

• Look for acute onset of redness, warmth, swelling, and tenderness at the ankle 3.
• The redness typically spreads outward from the initial site and may have poorly defined borders 4.
• You may develop fever, chills, or feel generally unwell, though these systemic symptoms are not always present early in the infection 5.
• Measure and mark the border of the redness with a pen so you can track whether it is expanding or shrinking with treatment 6.

When to Seek Immediate Medical Attention

Go to the emergency department immediately if you develop any of these warning signs 1:

• Severe pain that seems worse than the visible redness would suggest
• Rapid spread of redness over hours rather than days
• Skin that feels "wooden-hard" or develops blisters, purple discoloration, or black areas
• Fever above 38°C (100.4°F) with rapid heart rate (>90 beats/min) or rapid breathing (>24 breaths/min)
• Confusion, dizziness, or feeling faint
• Nausea or vomiting

Standard Antibiotic Treatment

• For typical ankle cellulitis, you will receive a beta-lactam antibiotic such as cephalexin 500 mg four times daily or dicloxacillin 250–500 mg every 6 hours for exactly 5 days 1.
• This treatment achieves approximately 96% clinical success because it targets the bacteria that cause typical cellulitis 1, 2.
• Extend treatment beyond 5 days only if your warmth, tenderness, and redness have not improved—do not automatically take antibiotics for 7–10 days 1.

When MRSA Coverage May Be Needed

Your doctor will add antibiotics that cover methicillin-resistant Staphylococcus aureus (MRSA) only if you have specific risk factors 1:

• Visible pus or drainage from the infection site

• Recent penetrating injury to the ankle (such as a puncture wound)

• History of injection drug use

• Known MRSA infection in the past or positive nasal swab for MRSA

• Fever with rapid heart rate and breathing (systemic inflammatory response)

• No improvement after 48–72 hours of standard antibiotics

• If MRSA coverage is needed, options include clindamycin 300–450 mg every 6 hours alone, or trimethoprim-sulfamethoxazole plus a beta-lactam, or doxycycline plus a beta-lactam 1.

Essential Home Care Measures

• Elevate your ankle above the level of your heart for at least 30 minutes three times daily—this promotes drainage of swelling and speeds healing 1, 7.
• Continue elevation even after antibiotics are started, as this adjunctive measure is often neglected but critical for recovery 1.
• Check between your toes for athlete's foot (tinea pedis), cracking, scaling, or moisture—treating these conditions reduces your risk of cellulitis coming back 1, 7.

Monitoring Your Response to Treatment

• You should see improvement within 24–48 hours of starting antibiotics—reduced warmth, less tenderness, and stabilization or shrinking of the redness 1.
• Contact your doctor if the redness continues to spread, pain worsens, or you develop fever after starting treatment 1.
• Some redness may persist for 1–2 weeks even after the bacteria are cleared, but warmth and tenderness should resolve within 5 days 1.

Preventing Recurrent Cellulitis

• Treat underlying conditions that increase your risk: chronic leg swelling (lymphedema), varicose veins (venous insufficiency), obesity, eczema, and athlete's foot 1, 8.
• Keep your skin moisturized and intact—dry, cracked skin provides entry points for bacteria 8.
• If you develop cellulitis 3–4 times per year despite treating these predisposing factors, your doctor may recommend preventive antibiotics such as penicillin twice daily 1.

What NOT to Do

• Do not assume you need MRSA coverage for typical ankle cellulitis—MRSA is uncommon in this setting even in areas with high MRSA rates 1, 2.
• Do not stop antibiotics early if you feel better after 2–3 days—complete the full 5-day course to prevent treatment failure 1.
• Do not delay seeking care if warning signs of severe infection develop—necrotizing infections progress rapidly and require emergency surgery 1.