First Aid for Spider Bites in North America

Most North American spiders do not produce venom that causes dangerous reactions when they bite. However, a bite from a black widow and the brown recluse spider can be fatal in rare cases. If you are a first aid respondent, your first aid training will help you identify the signs and symptoms of these spider bites.

Identifying a Black Widow Spider Bite

The black widow spider is black but can be identified by the marking on its underside which is a reddish hourglass shape. Only spider bites from a female black widow are toxic.

The patient might not immediately know that they have been bitten, even though a bite by a black widow usually causes sharp pain and burning on the area of the bite that then dulls. A bite from a black widow spider leaves two puncture marks on the skin.

Patients may start to feel ill or notice a bump or swelling some time after the bite. The swelling will be raised, red and round, and may be accompanied by cramps felt in the muscles of the thighs, abdomen, shoulders and back.

Other signs to look for include anxiety and restlessness, headaches, dizziness, excessive sweating and weakness. Also, look out for numbness and increased saliva and sweating.

Identifying a Brown Recluse Spider Bite

A spider bite from a brown recluse, also known as the violin spider, may not produce any pain initially. A stinging sensation may develop in the area up to eight hours later. The spider can be identified by its light brown body and its darker brown mark on the upper body that is violin-shaped.

The 1-inch long spider is not aggressive and will only bite when trapped against the patient’s skin. Often, the bite may be painless but will start to burn and itch up to eight hours later.

After a bite, a blood-filled blister may form on the surface of the skin that will resemble a target or bulls-eye pattern. Without treatment, the blister can get worse and even kill surrounding tissue.

Other reactions to look out for include nausea, vomiting and joint pain. These reactions can even occur up to 72 hours after the spider bite.

On rare occasions, a bite from a brown recluse spider may cause a coma, seizures, jaundice or kidney failure. A patient may also notice blood in their urine.

Medical treatment may include antibiotics and the wound needs to be kept clean. Tissue death only occurs rarely in extreme cases.

According to the government of Toronto, there has never been any verified record of the Brown Recluse spider living in Ontario.

High-Risk Areas for Spider Bites

The black widow spider and the brown recluse spider live in secluded spaces and are rarely disturbed. Most bites occur when the patient reaches into their dark hiding places. These can be in a piece of wood, brush pile, rock or dark storage spaces.