Which spider's bite can cause necrotic lesions?

The bite of a brown recluse spider can cause necrotic lesions. The brown recluse, Loxosceles reclusa, belongs to a group of spiders whose venom contains sphingomyelinase D, an enzyme associated with tissue destruction and the condition called loxoscelism.

Most suspected brown recluse bites do not become severely necrotic, and many produce only minor or self-healing reactions. In the more serious cutaneous form of loxoscelism, pain and itching may develop within hours, followed by worsening inflammation and tissue death over the next several days. The damaged area can form an ulcer that heals slowly and may leave a scar.

Brown recluses are reclusive and usually bite only when trapped against skin, such as inside clothing, shoes, bedding, or gloves. Their violin-shaped marking is widely known, but it is not by itself a reliable way to diagnose a bite.

A major common mistake is assuming that every unexplained necrotic wound came from a spider. Bacterial infections, especially MRSA, and several other medical conditions can look similar. A confirmed spider identification and professional medical evaluation are important, particularly when the wound spreads or systemic symptoms appear.