Redness from an insect bite that is spreading

Bites can trigger itch, redness, and swelling around the puncture. A reactive area may be itchy and gradually settle, while [Cellulitis](/conditions/cellulitis/) presents with infection in the skin and often becomes increasingly warm, tender, swollen, or painful. The edge can be marked with a pen to track change, but the size alone cannot diagnose the cause. Scratching may break the skin and introduce bacteria. A retained stinger, blister, discharge, or a rash appearing elsewhere changes the assessment. Describe the insect if known, the time of the bite, and any creams or medicines already used.

Gently clean the site, use a cool compress wrapped in cloth, and avoid scratching. Keep nails short and cover broken skin with a clean dressing. Do not apply household chemicals or squeeze a blister. If a clinician identifies a bacterial infection, [Antibiotics For Skin Infection](/treatments/medical-dermatology/antibiotic-therapy-for-skin-infection/) may be considered; do not start leftover medicine without advice.

Seek same-day advice when redness keeps advancing, becomes hot or painful, produces pus, or is accompanied by fever or swollen glands. Call emergency services for trouble breathing, throat or tongue swelling, widespread hives, faintness, or repeated vomiting after a bite.

Does this look like a bite reaction or cellulitis? Is any foreign material left in the skin? What symptoms should I watch for, and which treatments are safe with my medical history?