Black house spiders are unlikely culprits in necrotic arachnidism: a prospective study.

Twenty-five patients with definite bites by Badumna spp. spiders were recruited prospectively. Bites occurred across Australia, 92% from October to March, and most during daylight. Pain occurred in all cases, was severe in seven cases, with a median duration of 5 min. Other effects included: puncture marks (24%), swelling (12%) and erythema (68%). Minor systemic effects occurred in 4 bites. No patient had a necrotic ulcer (0%; 97.5% confidence interval 0-14%). Black house spiders (Badumna spp.) are unlikely to cause necrosis, contrary to reports of suspected bites. Patients can be reassured and do not require any further investigation or treatment.