Spider bites
Verified spider bite identification, clinical management, and the differential diagnoses most often confused with spider envenomation.
- Medical reference
How to identify a spider bite
Most lesions blamed on spiders are not spider bites. Clinicians and patients consistently misattribute bacterial infections, tick bites, and other skin conditions to spiders. This page covers what a verified spider bite actually looks like and the diagnostic standard used by toxicologists.
- Loxoscelism
Brown recluse bite: symptoms and treatment
Loxoscelism - the syndrome caused by Loxosceles envenomation - is rare even within the brown recluse's native range and is over-diagnosed. Most suspected cases outside the native range are not recluse bites.
- Latrodectism
Black widow bite: symptoms and treatment
Latrodectism is the syndrome caused by Latrodectus envenomation. Bites are uncommon but produce a characteristic pattern of severe muscle cramping. Antivenom is available and effective for severe cases.
- Differential diagnosis
Spider bite vs. MRSA infection
The most common misdiagnosis for a 'spider bite' is community-acquired MRSA. This page covers the clinical signs that distinguish the two and why the distinction matters.
- Risk overview
Are spider bites dangerous?
For the average person in North America, spider bites are very rarely dangerous. Only two genera - Latrodectus (widows) and Loxosceles (recluses) - produce verified medically significant envenomation in the US.
- Medical reference
Necrotic arachnidism: scope and overdiagnosis
Necrotic skin lesions attributed to spiders are overwhelmingly caused by other agents. In the United States, the only spider conclusively linked to dermonecrosis is Loxosceles reclusa and a small number of related Loxosceles species in the south-central states.
- Medical reference
Antivenom for widow envenomation
Latrodectus antivenom (Antivenin Latrodectus mactans, Merck) is effective at relieving systemic latrodectism but is reserved for severe or refractory cases due to the risk of acute hypersensitivity and serum sickness.
- Medical reference
Pediatric spider bite assessment
Children present a higher risk profile for severe latrodectism and systemic loxoscelism. Documented bites in children warrant lower thresholds for emergency evaluation and longer observation periods.
- Medical reference
Tetanus and secondary infection after presumed bites
For any puncturing arthropod injury, tetanus status review and wound hygiene are standard. Secondary bacterial infection is more common than systemic envenomation and is the principal cause of morbidity after most presumed spider bites.