Spider Bites: Can They Kill You?

You’ve probably heard it before. We’ll have to repeat it here. Spiders are really good guys. They eat mosquitoes, flies, and other annoying bugs. They reportedly save us billions of dollars in pest control — and that’s especially helpful in the agricultural business.

In some countries, spiders are considered good food. But admittedly, they are ugly to the human eye. We are more inclined to kill them than to escort them outside. And some of them do bite.

But there are only two species in the United States that can cause bodily harm with their bites: the black widow spider (Lactrodectus) and the brown recluse or fiddleback spider (Loxosceles). “Fiddleback” refers to the violin shaped back of this spider.

The brown recluse is considered by some experts to be the most dangerous spider to humans. But in their defense, remember they eat cockroaches, silverfish and other soft-bodied insects. Not all states even have this type of spider. They are most common in the western, central, and southern states.

As the name suggests, the brown recluse spider tries to avoid contact with humans. They tend to hide out in basements and dark corners. You are most likely to get bitten when putting on clothes or shoes that were left on the floor.

The spider crawls into the warm, dark material (or shoe). You put the article of clothing on without thinking to check for unwanted guests. And the spider reacts to the sudden movement with its only defense: a bite. Spider bites that are present when you wake up in the morning occur when the spider climbs up covers that touch the floor. If you move or roll onto the spider, you get the same defensive response: a bite.

The female black widow is commonly recognized by its black color, hour glass shape and red markings. Males are smaller, usually have yellow and red bands and spots over the back, and don’t bite. Although they live in warmer climates (and desert areas), they can be found in states with cooler temperatures.

The female black widow spider is probably the most venomous spider in North America. But it injects a very small amount of venom (poison) when it bites. Very few people actually die of spider bites.

The bite of the brown recluse or black widow can cause local effects (pain, redness of the skin, an open wound) or systemic effects. In a very small number of people, deep wounds can develop from infection. The result can be necrosis (tissue death). For those patients, surgery might be needed to help deep wounds heal.

The systemic symptoms are caused by the neurotoxic effects of the venom. Neurotoxins primarily target the nervous system. Systemic symptoms can include muscle cramping, sweating, nausea, vomiting, fever, chills, and dehydration. In less than one per cent of cases, the reaction can be severe enough to cause paralysis, respiratory arrest, and even death.

Whenever dealing with spider bites, the best advice is to capture the spider (if possible) for identification and seek medical advice right away. Most of the time, local treatment of the skin is all that’s required. A tetanus shot may be needed. Hospitalization is only necessary when there is a severe reaction with dehydration and/or compromise of the heart or lungs. Antibiotics are not used unless infection develops.

Antivenin (an antidote to the poison) is not given routinely because symptoms go away quickly (within several hours to several days). Although there is a specific antivenin for brown recluse spider bites, it is not available in the United States. There aren’t very many studies on the subject, but research evidence does not support the use of antivenin to prevent skin necrosis.

To avoid spider bites, the best advice is to keep all clothes and bedclothes off the floor. To keep spiders out of bed with you, don’t use a dust ruffle around the bottom of the bed. This just gives the spider a “leg up” so-to-speak. And don’t throw the sheets, blankets, or covers on the floor.

Check your shoes before putting them on. When working outdoors, wear gloves and beware of spiders when picking up those gloves or other tools if they have been sitting in a shed, garage, or other dark storage area.

Despite all the photos you can find on-line of the severe local effects of some spider bites, these cases are really rare. Death from spider bites is even more unusual.