What should I do if I was stung on the knee and now my knee and leg are swollen?

Immediate Management of Insect Sting with Knee and Leg Swelling

You are experiencing a large local allergic reaction to an insect sting, which requires anti-inflammatory treatment—not antibiotics—and should improve within a week with proper care. 1

What You're Experiencing

This is an IgE-mediated allergic reaction causing extensive swelling that typically peaks at 24-48 hours after the sting and can last up to a week or more. 2, 1 The swelling extending from your knee down your leg is caused by allergic inflammation and mediator release, not by infection, despite how concerning it may look. 2, 1

Immediate Steps to Take Now

First Priority: Remove the Stinger

• Scrape or flick away any visible stinger immediately—do not squeeze or pull it, as this can inject more venom. 2 The amount of venom delivered corresponds directly to how long the stinger remains embedded in your skin (up to 30 seconds). 2

Reduce Swelling and Pain

• Apply ice or cold packs to the affected area to reduce local pain and swelling. 2
• Elevate your leg above heart level to reduce swelling and improve circulation. 3
• Take oral antihistamines (like diphenhydramine or cetirizine) to reduce itching, pain, and inflammation. 2
• Use over-the-counter pain relievers such as acetaminophen or ibuprofen for pain control. 2

Critical Warning: Do NOT Take Antibiotics

The most common mistake is confusing this allergic swelling for bacterial cellulitis and taking unnecessary antibiotics. 1 The extensive redness and swelling—even if it includes red streaking (lymphangitis)—is caused by mediator release from the allergic reaction, not infection. 2, 1

Antibiotics are only indicated if you develop clear signs of secondary bacterial infection, such as: 2, 1

• Purulent (pus) drainage from the sting site
• Fever developing after 48-72 hours
• Progressive worsening beyond 48-72 hours despite anti-inflammatory treatment

When to Seek Emergency Care Immediately

Go to the emergency department or call 911 if you develop any of these systemic symptoms: 2, 4

• Difficulty breathing or throat tightness
• Tongue or throat swelling
• Dizziness or feeling faint
• Widespread hives beyond the sting area
• Nausea, vomiting, or abdominal pain
• Rapid heartbeat or chest pain

These would indicate anaphylaxis requiring immediate epinephrine administration. 2

Expected Timeline and Follow-Up

• Your swelling will likely continue to increase for the next 24-48 hours before it starts improving. 2
• Complete resolution typically takes 5-10 days. 2
• Monitor for signs of vascular compromise: increasing pain, numbness, coolness of your leg, or color changes that worsen despite treatment. 3 If these occur, seek emergency evaluation.

Consider Oral Corticosteroids

If the swelling is severe or causing significant functional impairment, contact your healthcare provider about a short course of oral corticosteroids (like prednisone), which can rapidly reduce inflammation. 2, 1, 3 While definitive proof of efficacy is lacking from controlled trials, many physicians use them for severe large local reactions. 2

Future Prevention

• You have a 5-10% risk of developing a systemic (whole-body) allergic reaction to future stings. 2, 4
• Consider asking your doctor for a prescription epinephrine auto-injector to carry with you, especially if you have frequent outdoor exposure. 2, 3
• If you experience repeated severe local reactions or have unavoidable frequent exposure to stinging insects, referral to an allergist for evaluation and possible venom immunotherapy may be appropriate. 2, 3, 4