A toxic reaction occurs when insect or spider venom acts like a poison in the body. This type of reaction can occur from one bite or sting from a highly toxic insect or spider, or from multiple bites or stings from insects or spiders not normally considered poisonous.

Symptoms of a toxic reaction vary depending on the insect or spider, the toxicity of the venom, and the amount of venom injected. Most often symptoms lessen or go away within 48 hours. Although hives and difficulty breathing may occur in an allergic reaction, these symptoms will not occur in a toxic reaction. It is possible to have both a toxic reaction and an allergic reaction at the same time.

Signs and symptoms of a toxic reaction may include:

• Nausea or vomiting.
• Diarrhea.
• Fever.
• Weakness.
• Lightheadedness.
• Rapid swelling at the site of the sting.
• Muscle spasms.
• Headache.
• Drowsiness.
• Fainting (syncope).
• Uncontrollable jerking movements (seizures).

A toxic reaction may lead to heart rhythm problems, shock, and death.