Spider bite

Most spiders are harmless

Symptoms of spider bite

Potentially lethal spiders

Remedies / treatment for spider bite

References

Most spiders are harmless

There are about 40,000 known species of spiders, of which only 200 have serious, potentially lethal bites. (1) Most spider bites occur when someone unintentionally brushes against or touches a spider and gets a defensive bite. On rare occasions a spider may mistake a finger or other body part for prey, as if it were a caterpillar or other insect. Many spiders do not have mouthparts capable of penetrating human skin. Only the larger spiders have fangs long enough to penetrate human skin. Most spider bites are not even noticed. Of those that are noticed, 98% have no serious medical consequences.

Two types of spider bites are harmful and/or painful. Most common are those bites that inject sufficient harmful venom. The amount of venom injected with a bite can vary a lot, even with the same spider. The other cause is harmful infections, which occurs in less than 1% of bites.

Spider venom is usually neurotoxic - meaning containing chemicals which attack the nervous system. Different venoms from different spiders can act in different ways. Venomous bites can be painful, and in the worst cases can stop breathing and the heart. A very few spiders have a venom that is so toxic that a single bite can cause death.

Other spider venoms contain necrotic agents that damage and destroy cells. Usually necrotic venoms attack tissues surrounding the bite, but in a few cases they may affect other organs.

Symptoms of spider bite

• Many spider bites, including those by some dangerous species, are relatively painless at first and may go unnoticed if you don't actually see the spider.
• Pain. Non-venomous: lasting 5-60 minutes. Venomous: lasting a day or longer.
• Abdominal cramps.
• Muscle spasms.
• Paralysis.
• Breathing may be affected.
• Allergic reactions up to and including anaphylactic shock can occur in a some people.
• Necrotic venom bites usually take 2-8 hours to become painful and itchy, with the pain and other local effects worsening 12 to 36 hours after the bite, and then necrosis develops over the next few days. Sometimes there is nausea, vomiting, fever, rashes, and muscle or joint pain immediately after the bite.
• Necrotic venom causes large open sores that can take many months to heal. They can leave deep scars, and may require a skin graft. In the worst cases the wound can be 25 cm / 10" wide.

Potentially lethal spiders

Neurotoxic

Funnel web spider. Found on the east coast of Australia.

Black widow spider. Various widow spiders are found on every continent except Antarctica. The single species occurring in Australia is commonly called the redback.

Brazilian wandering spider (Banana spider). Found mainly in tropical South America.

Mouse spider. There are eleven known species. Ten are Australian, one is from Chile.

Necrotic

Spiders with necrotic venom often come from the family Sicariidae, which includes both the recluse spiders (violin spiders, fiddlers or fiddlebacks) and the six-eyed sand spiders. Different species of recluse spiders are found in warmer climates worldwide. Six-eyed sand spiders are found in deserts and sandy places in southern Africa.

Remedies / treatment for spider bite

• If you are bitten by a spider, it will help if you can capture the spider to assist with identification and the correct treatment. Of course, don't risk another bite! A dead spider may also be identified if not too squashed. If you have a camera, a close-up photo is also helpful.
• Wash the bite with soap and water.
• Apply half a drop of iodine directly on the bite. This will prevent infection and may counteract the spider venom if you apply it quickly enough after the bite.
• Apply ice to reduce inflammation.
• Gum turpentine applied to the skin will soothe the bite area.
• See details of remedies recommended by Grow Youthful visitors, and their experience with them.

References

1. Diaz, James H. The global epidemiology, syndromic classification, management, and prevention of spider bites. 1 August 2004. American Journal of Tropical Medicine and Hygiene 71 (2): 239-250. PMID 15306718.