In the U.S., most spiders you will find are harmless, but the black widow spider and the brown recluse spider are exceptions. Both types of spiders are more common in the southern U.S. and in warm, dry climates. Within these areas they tend to be found in environments that are undisturbed such as basements, closets, attics, under sinks, or in wood piles.
The bite of a black widow spider is dangerous because it can affect a person’s nervous system. The spider produces a neurotoxic protein that is extremely potent. Some people may have a minimal reaction, but others may suffer from a severe response.
Symptoms of a black widow spider bite start within an hour after being bitten. Symptoms include severe muscle cramps, abdominal pain, weakness, and tremor. In severe cases symptoms may include nausea, vomiting, faintness, dizziness, chest pain, and respiratory difficulties.
Another toxic spider is the brown recluse, whose venom is more potent than that of a rattlesnake, and is toxic to cells and tissues. However, because the bite releases much smaller quantities of poison into its victims, brown recluse bites cause less damage than rattlesnake bites.
Brown recluse spider bites may not even be noticed at first as they are often painless. Some people may notice minor stinging such as that felt with a bee sting when bitten by the spider. Symptoms of a brown recluse spider bite develop within eight hours after being bitten and include severe pain at the bite site, severe itching, nausea, vomiting, fever, and muscle pain.
The black widow spider gets its name from the erroneous belief that the female spider kills the male after mating. There are five species of black widow spiders in the U.S.; the southern black widow and the northern black widow are the most common. The spider is medium-sized and about half-inch long.
The southern black widow spider is one of the two commonly found species of black widow spiders found in the U.S. and can be identified by its shiny, black, globular abdomen with the distinctive red hourglass shape on its underside.
The northern black widow spider doesn’t have the hallmark red hourglass shape on its belly, instead it can be identified by a row of red spots (spots may also be yellow or white) down the middle of the upper surface of its abdomen, and two crosswise bars on the undersurface. The spider may be brown or have red legs.
Brown recluse spiders are native to the U.S. Midwest and Southeast. It is rare to find them outside these areas. There are 13 other species of spider in the same family that may be falsely identified as a brown recluse.
Spiders in the same family as the brown recluse spider include the desert recluse found in Texas, Arizona, and California, and the Arizona recluse. Bites from these spiders may cause some localized skin disease, but no deaths have been reported from non-brown recluse spiders.
Brown recluse spiders are identified by their characteristic violin pattern on the back of the cephalothorax (the part of the body where the legs attach). The base of the violin appears to be at the head of the spider and the neck of the violin points to the rear. Brown recluse spiders are small with one-inch legs, non-hairy, yellow-tan to dark brown in color, and darker legs. Most spiders have eight eyes, but the brown recluse has just six – it belongs to the genus Loxosceles. This feature is usually too small for people to see with the naked eye.
Black widow spiders are active at night (nocturnal), and they prefer dark areas. They tend to avoid houses where people live, but they may be found in garages or sheds. Only female black widow spiders bite humans, and they only do so if disturbed.
Brown recluse spiders are not aggressive and will only bite if they feel threatened. They prefer dark, warm, dry environments such as attics, closets, basements, barns, and wood piles. Most brown recluse bites occur during the summer. The spider searches for prey at night and rests in the day in its small web, which is usually constructed in corners or crevices.
A black widow spider bite may appear as double fang marks at the site of the bite. The bite is described as feeling like a pinprick, though there may only be a small localized reaction. Blood pressure or heart rate may rise. The severity of the reaction to the bite depends on the age and overall health of the victim. Children and the elderly are usually more seriously affected.
Hours after being bitten by the black widow spider, the bite injury will swell. In the case pictured, two days after being bitten the redness and swelling continued past the elbow and down the forearm of the victim. Eight days after the bite, the swelling went down, the bite opened, and the infection was nearly gone.
A brown recluse spider bite may appear slightly red and when you look closely you may see fang marks. In most cases, the bite site will become firm and will heal over the following days to weeks with minimal scarring. In some cases the local reaction will be more severe with redness, blistering, blue discoloration, tissue death, and scarring. Pictured: the bite area swelled to quarter-size within an hour, and within a day continued to swell, turning blue and dark red.
In severe cases, the reaction to a brown recluse spider bite can lead to death of the skin (necrosis) and subcutaneous fat. Pictured: the same patient as in the previous slide, after three days, with initial stages of skin necrosis.
As the reaction to the brown recluse spider bite progresses, severe necrotic lesions with deep, wide borders can result. Pictured: the same patient in the previous slides, eight days following the bite. The wound remained open the entire time for the spider’s toxins to drain, and the patient needed constant intravenous antibiotics and pain medications.
Eleven days after the brown recluse spider bite a five-inch wide area of dead tissue was removed, and a skin graft was needed. Pictured: skin graft results 38 days after the bite.
Pictured: Ten months after the brown recluse bite, the wound is healed, with scarring.
Seek care immediately following a black widow spider bite at a hospital emergency department. Most doctor’s offices or urgent care centers are not equipped to deal with these types of injuries. Treatment for pain may require narcotic pain relievers and antivenin to counter the effects of the spider venom, which can usually only be found in a hospital setting.
For minor black widow spider bites, home care treatments are limited. Cold or awarm compresses and hot baths may help ease pain. Over-the-counter pain relievers such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) may help for mild bites. Folk remedies do not work.
If you think you have been bitten by a brown recluse spider see a doctor immediately or go to a hospital emergency department. If possible, bring the spider to the doctor’s office so the physician can identify the spider to help make the proper diagnosis.
Clean the wound area thoroughly with soap and water first, and then seek medical care. Home care is for relief of symptoms only after you have been treated by a doctor. Apply ice to decrease pain and swelling, and take acetaminophen (Tylenol) for pain. Elevate the area above the heart if possible. Avoid strenuous activity which can spread the spider venom through the skin.
Be cautious of both black widow spiders and brown recluse spiders if bitten. Both can cause painful bites, which can be deadly in some cases. The brown recluse spider bite can cause severe blistering, blue discoloration, and necrotic lesions with scarring. However, the black widow spider bite can cause severe neurological symptoms especially in children or the elderly. Both types of spiders can be dangerous, and you should seek medical attention if bitten by either type of spider.