What Are the Symptoms of a Black Widow Bite?

Muscle pain and cramping are the hallmark. The Defense Centers for Public Health says muscle and chest pain or tightness are the most common reactions to widow spider venom, that the pain may spread to the abdomen with cramping and nausea, and that in severe cases the toxin can cause breathing and speech difficulty, heart irregularities and even death from suffocation. A July 2026 US military clinical guideline says some people do not develop systemic toxicity, but in those who do, symptoms typically begin 15 to 60 minutes after the bite with painful muscle cramping that starts at the bite site and moves toward the center of the body, and that a rigid abdomen from muscle spasm may be mistaken for peritonitis.

The Defense Centers for Public Health says the southern black widow ranges as far north as New York, south to Florida and west into Texas, Oklahoma and Kansas, and is also found in California and throughout the deserts of the American Southwest, while the western black widow ranges from west Texas, Oklahoma and Kansas westward through the Pacific coast states to the adjacent Canadian provinces.

After a spider bite, CDC's NIOSH advises washing the area with soap and water, applying a cloth dampened with cold water or filled with ice to reduce swelling, elevating the area if possible, not attempting to remove venom, and seeking professional medical attention. The Defense Centers for Public Health says to bring the spider to the hospital for identification if it can be safely contained, and that antivenom is available for southern black widow bites.

Antivenom is debated. The military guideline says antivenom, if available, may be indicated for severe pain that does not respond to pain medication but may not be readily available, that rare fatal allergic reactions to it have occurred, and that long-term injury or death from widow spider bites is extremely unlikely. A 2017 systematic review in Toxins says antivenom with opioid pain relief is often the main treatment reported, but that recent high-quality evidence has cast doubt on the clinical effectiveness of that combination.