T63.311A Toxic effect of venom of black widow spider, accidental (unintentional), initial encounter

ICD-10-CM T63.311A: Toxic effect of venom of black widow spider, accidental (unintentional), initial encounter

ICD-10-CM code T63.311A represents the toxic effect of black widow spider venom for an accidental and unintentional initial encounter. Black widow spiders produce a highly toxic venom that acts as a neurotoxin, causing pain that can spread to the chest, abdomen, or entire body. This reference outlines clinical characteristics and code distinctions based on public source excerpts. 4 5 3

Plain-language overview

The black widow spider has a shiny black body and produces a highly toxic venom that interferes with chemicals in nerve endings. This venom is a neurotoxin that produces pain at the bite area and then spreads to the chest, abdomen, or the entire body. 5 3

What this code represents

Code T63.311A represents the toxic effect of venom of black widow spider, accidental (unintentional), initial encounter. This code is distinct from T63.301A, which designates the toxic effect of unspecified spider venom, accidental (unintentional), initial encounter. 4 6

Code T63.311A is also distinct from T63.331A, which represents the toxic effect of venom of brown recluse spider, accidental (unintentional), initial encounter. Both T63.311A and T63.331A apply to initial encounters that are accidental and unintentional. 6

Clinical context

Clinical diagnosis of a black widow spider bite depends mainly on medical history, wounds, non-specific clinical manifestations, and corresponding epidemiological findings. Visualizing the bite along with its associated symptoms and obtaining a detailed history will allow accurate diagnosis. 1

To officially confirm the diagnosis, the patient must bring in the spider after witnessing the bite and an entomologist, medical toxicologist, or another qualified specialist must identify the spider. It is not recommended for patients to capture, harm or handle the spider. 1

Black widow spider envenomation frequently results in severe pain, muscle cramps, abdominal pain, back pain, and hypertension. Severe abdominal pain mimicking an acute abdomen has even been reported, and symptoms can be extremely uncomfortable. 2

Documentation considerations

The clinical characteristics of black widow spider bites are diverse, and symptoms of envenomation range from local irritation and pain to a systemic syndrome termed latrodectism. Latrodectism is characterized by variations in presentations ranging from autonomic disturbance to widespread pain and rigidity. 1

What the sources add

The CDC notes that spiders are usually not aggressive and most bites occur because a spider is trapped or touched, while the clinical report adds that patients were all bitten in places like grasslands, deserts, farmlands, stone seams, earth caves, and hay. 3 1

The Cleveland Clinic states that a female black widow spider bite can be dangerous, while the CDC notes that black widows are venomous spiders found in the United States that can be dangerous to outdoor workers. 5 3

Sources

1. Clinical characteristics of patients with black widow spider bites: A report of 59 patients and single-center experience — pmc.ncbi.nlm.nih.gov; accessed 2026-07-26.
2. The Treatment of Black Widow Spider Envenomation with Antivenin Latrodectus Mactans: A Case Series — pmc.ncbi.nlm.nih.gov; accessed 2026-07-26.
3. Venomous Spiders at Work — cdc.gov; accessed 2026-07-26.
4. EVS Explore — evsexplore.semantics.cancer.gov; accessed 2026-07-26.
5. Black Widow Spider Bite — my.clevelandclinic.org; accessed 2026-07-26.
6. Spider Bite ICD-10-CM Codes — carepatron.com; accessed 2026-07-26.