What should you know about spider bite bullseye rash?

A ring or target-like mark can reflect local irritation, an allergic response, or another skin condition. The center may look different from the outer edge, and the pattern can change over time. A rash is a symptom, not proof that a spider caused it. Other possibilities include contact dermatitis, heat rash, ringworm, scabies, psoriasis, atopic dermatitis, intertrigo, or a drug rash.

Take a clear photograph with the date and note when the mark began, whether it is enlarging, and any new products, medicines, travel, or outdoor exposure. Wash the area gently and avoid squeezing, burning, or applying harsh chemicals. Do not start a prescription cream based only on a photograph; an examination may be needed to distinguish an infection from inflammation or fungus.

Seek prompt medical advice if the rash is expanding, painful, hot, blistering, draining, or accompanied by fever or feeling unwell. Get urgent help for facial swelling, breathing difficulty, confusion, or a rapidly worsening widespread rash. A clinician should assess a target-like rash that persists or changes, especially when the bite was not witnessed.

What features make this rash more consistent with irritation, infection, or another condition? Does it need a skin test or treatment? Which changes should make me return urgently?