Side Effects of a Black Widow Spider Bite

The female black widow spider is considered the most venomous spider in North America. The black widow can be identified by the distinctive hourglass shaped red marking on the abdomen. The venom of the black widow is a neurotoxin, meaning it affects nerves and nerve tissue.


When a person is bitten by the black widow, he may experience an immediate pinprick sensation. According to "Sheehy's Emergency Nursing Principles and Practice," the person develops cramping and spasms in the local muscle groups near the site of the bite, which then spreads to a larger area of muscle groups.

Onset of Symptoms

Two tiny red fang marks appear at the site where the bite occurred. A local reaction occurs within minutes, and the pain seems out of proportion to the size of the bite. Systemic reactions occur within one hour; the person could develop breathing problems, weakness and chest pain. The person may seem to be unaware of her surroundings. In some instances, seizures and shock can develop. Symptoms peak two to three hours after onset but can last several days.


When a person is bitten by a spider, he should immediately clean the wound, apply a snug bandage above the bite to slow the spread of the venom and seek medical treatment, according to Applying ice to the area of the bite helps slow the spread of the venom. Medical treatment focuses on treating the symptoms. Medications may be given to control the pain and muscle spasms. A spider anti-venom is available, which can shorten the course of the effects. If anti-venom is used, there is a risk the patient could have a severe allergic reaction to it.


Most patients do not require hospitalization, and the symptoms subside in two to three days. Even with the use of anti-venom, patients may have fatigue, weakness and other non-specific symptoms that can last up to 10 days. Patients who are very young, very old or have cardiac disease are at increased risk of developing complications and may require hospitalization.

Geographic Location

The black widow spider is found in every state of the United States except Alaska. These spiders are not aggressive and will bite only when disturbed. They usually are found in their webs, which are often located in protected places such as under stones and in woodpiles.