What should you know about cellulitis from a flu shot?

After a flu shot, mild soreness, warmth, or limited swelling around the injection site can occur. Cellulitis is different: redness, warmth, pain, or swelling may keep expanding and can extend beyond the injection area. A clinician should assess a worsening reaction, especially if you develop Fever or feel unwell. The timing alone cannot confirm that the injection caused an infection.

Clean the area gently with soap and water, cover any open skin, and avoid scratching, squeezing, cutting, or trying to drain it. Raise an affected arm or leg when practical if swelling is uncomfortable. Do not use leftover antibiotics or another person's medicine. Contact a clinician promptly if redness expands, the skin becomes hot or painful, or fluid drains from it. Explain when the trigger occurred and how the area has changed.

Seek urgent help for rapidly spreading redness or swelling, severe pain, Fever, shaking chills, faintness, confusion, breathing difficulty, or a purple or blistered area. Get earlier advice for changes near the eye, face, or a joint, and if you have Type 2 Diabetes or reduced immune defences. A worsening infection can extend into deeper tissue or the bloodstream; sudden severe illness can signal Sepsis.

Ask whether the area resembles a local reaction or Cellulitis, whether prescription treatment is needed, how to care for any wound, and which changes should prompt same-day review. Ask what improvement should look like after treatment begins.