Venomous Bites and Stings

Certain animals can inject venom (poison) through mouth parts or a stinging apparatus. These animals usually do not bite or sting a per-son unless they are provoked or otherwise disturbed in some way.

Poisonous Snake Bites

About 25 species of venomous (poisonous) snakes are native to the United States. They include pit vipers (rattlesnakes, copper-heads, and cottonmouths), coral snakes, and a few species of rear-fanged snakes (colubrids). Although more than 45,000 people are bitten by snakes in the United States each year, fewer than 8,000 bites by venomous snakes are reported, and fewer than 15 people die. Most deaths occur in children, the elderly, people who are untreated or treated in appropriately, and people belonging to religious sects in which members handle poisonous snakes. Rattlesnakes account for about 70 per cent of poisonous snake bites in the United States and for almost all of the deaths. Copperheads, and to a lesser extent cottonmouths, account for most other poisonous snake bites. Coral snakes inflict less than 1 percent of all bites. Imported snakes found in zoos, snake farms, and amateur or professional collections account for about 15 bites a year.

A poisonous snake bite doesn't always result in snake venom poisoning. Venom is not injected in about 25 percent of all pit viper bites and about 50 percent of cobra and coral snake bites. Snake venom is a complex mixture containing many proteins that trigger harmful reactions. Snake venom can affect every major organ system in the body directly or indirectly.

The venom of rattlesnakes and other pit vipers damages tissue around the bite, produces changes in blood cells, prevents blood from clotting, and damages blood vessels, causing them to leak. These changes can lead to internal bleeding and heart, respiratory and kidney failure. The venom of coral snakes affects nervous system activity but causes little damage to tissue around the bite.

Symptoms and Diagnosis

The symptoms of pit viper poisoning vary widely, depending on the size and species of snake, the amount and toxicity of the venom injected, the bite's location, the victim's age and size, and the presence of other medical problems. Most bites occur on the hand or foot. Usually, bites by rattlesnakes, cottonmouths, and copper-heads cause pain immediately after the venom is injected; swelling follows within 10 minutes. These symptoms are rarely delayed more than 20 to 30 minutes. The pain can vary from mild to severe. A poisonous bite can be diagnosed on the basis of fang marks, redness, pain, swelling, and tingling and numbness in the fingers or toes or around the mouth, among other symptoms. A metallic or rubbery taste in the mouth has been noted after bites by some species of rattlesnakes.

If untreated, the swelling can progress, affecting the entire leg or arm within several hours. The lymph nodes in the area may also swell and may be painful. Other symptoms include fever; chills; general weakness; a rapid, weak heartbeat; faintness; sweating; nausea; and vomiting. Breathing difficulties can develop, particularly after Mojave rattlesnake bites. The victim may have a headache, blurred vision, drooping eyelids, and a dry mouth.

Moderate and severe pit viper poisoning commonly causes bruising of the skin, which may appear 3 to 6 hours after the bite. The skin around the bite appears tight and discolored: blisters may form in the bite area within 8 hours and often fill with blood. Without treatment, tissue destruction around the bite may occur, with blood clots forming in the surrounding blood vessels.

The venom of many pit vipers, particularly rattlesnakes, prevents blood from clotting; the gums may bleed and blood may appear in the vomit, stools, and urine. The results of blood tests that assess clotting may be abnormal, and the number of platelets (the blood components responsible for clotting) may be markedly reduced.

Coral snake bites usually cause little or no pain and swelling. The main symptoms are caused by changes in the nervous system. The area around the bite may tingle, and nearby muscles may become weak. Muscle incoordination and severe general weakness may follow. Other symptoms include visual disturbances and increased saliva production, with speech and swallowing difficulties. Breathing problems, which may be extreme, may follow.


Poisonous snake bites are medical emergencies requiring immediate attention. Before starting treatment, emergency medical personnel must try to determine whether the snake was poisonous and whether venom was injected. If no venom was injected, treatment is the same as for a puncture wound-thorough cleaning and a tetanus booster.

Anyone bitten by a pit viper should be kept as calm and still as possible, kept warm, and taken to the nearest medical facility immediately. The bitten limb should be loosely immobilized and kept positioned below heart level. Rings, watches, and tight clothing should be removed, and no stimulants should be given. A Sawyer's extractor (a device that suctions venom from the site of the bite, designed for first aid) should be applied over the bite within 5 minutes and kept in place for 30 to 40 minutes during transportation to the hospital for further treatment.

Venom antidote (antivenom), which neutralizes the venom's toxic effects, is an important part of treatment for most bites. Antivenom is given intravenously. Atetanus booster is also given, and antibiotics are occasionally needed.

The general treatment of coral snake bites is the same as for pit viper bites. If breathing problems develop, respiratory assistance may be needed. Antivenom may be needed; one that's specific for coral snake bites is used.

In all cases of snake bite poisoning, particularly in children and the elderly, a Poison Control Center should be contacted. The local zoo or poison center should be the first place to call for advice on treating a bite by an imported poisonous snake. Personnel at these locations know where to obtain antivenom and have a directory of doctors who specialize in treating these bites.

Poisonous Lizard Bites

The only two lizards known to be poisonous are the beaded lizard of Mexico and the Gila monster, found in Arizona and Sonora, Mexico, and adjacent areas. The venom of these lizards is somewhat similar in content and effect to that of some pit vipers.

Common symptoms include pain, swelling, and discoloration in the area around the bite as well as swollen lymph nodes. Weakness, sweating, thirst, a headache, and ringing in the ears (tinnitus) may develop. In severe cases, blood pressure may fall. Treatment is similar to that of pit viper bites. A specific antivenom is not available.

Spider Bites

Almost all spiders are poisonous. Fortunately. the fangs of most species are too short or too fragile to penetrate human skin. Nevertheless, at least 60 species in the United States have been implicated in biting people. Species not native to the United States may be brought into the country on fruits, vegetables, or other materials.

Although tarantulas native to the United States are considered dangerous, their bites do not seriously harm people. On the average, spider bites cause fewer than three deaths a year in the United States, usually in children.

Only a few spider venoms have been studied in detail. The venoms studied are complex, containing enzymes and other proteins that cause various reactions in the body.


The bite of a black widow spider usually causes a sharp pain, somewhat like a pinprick, followed by a dull, sometimes numbing, pain in the area around the bite. Cramping pain and muscular stiffness in the abdomen or the shoulders, back and chest also develop. Other symptoms may include restlessness, anxiety, sweating, headaches dizziness, drooping and swelling of the eyelids skin rash and itching, severe breathing problems nausea, vomiting, increased saliva production and weakness. The skin around the bite may fee warm.

The bite of a brown recluse spider may cause little or no immediate pain, but some pain, develops in the area around the bite within an hour, or so. Pain may be severe and may affect the entire injured area. The area around the bite becomes red and bruised and may itch. The rest of the body may also itch: A blister forms, surrounded by either an irregular bruised area or a more distinct targetlike red zone.

The area appears first as a bull's-eye: Then the blister enlarges, fills with blood, and ruptures, forming an open sore (ulcer) that may leave a large craterlike scar. Nausea, vomiting, aches, fatigue, chills, sweats, blood disorders, and kidney failure may develop, but the bite is rarely fatal.


The only first-aid measure of any value for a black widow spider bite is placing an ice cube on the bite to reduce pain. People under 16 or over 60 years of age and those who have high blood pressure and heart disease are usually hospitalized for treatment. Antivenom, which neutralizes the effects of the toxin, is given for severe poisoning.

Other measures may be needed to treat breathing difficulties and extremely high blood pressure. Muscle pain and spasms can be relieved by muscle relaxants. Pain can be relieved in mild cases by hot baths and in severe cases by narcotic analgesics.

For brown recluse spider bites, ice placed on the bite helps reduce pain. Corticosteroids are usually given to reduce inflammation. An anti-venom is not yet commercially available.

Skin sores are cleaned daily with hydrogen peroxide and soaked three times a day; dead tissue is trimmed away as needed. For most bites, this treatment is all that's needed.

Bee, Wasp, Hornet, and Ant Stings

Stings by bees, wasps, hornets, and ants are common throughout the United States. The average person can safely tolerate 10 stings for each pound of body weight. This means that the average adult could withstand more than 1,000 stings, whereas 500 stings could kill a child. However, one sting can cause death from an anaphylactic reaction in a person who is allergic to such stings.

In the United States, three or four times more people die of bee stings than of snake bites-very year. The few fatalities from multiple bee stings are usually caused by heart malfunction and collapse of the circulatory system.

A more aggressive type of honeybee, called the Africanzed killer bee, has reached some southern states as these bees travel north from South America. By attacking their victim in swarms, these bees cause a more severe reaction than do other bees.

Dangerous Spiders

Black widow spiders and related species

Brown or violin spiders, sometimes called brown recluse,

and related species

jumping spiders

Tarantulas (not native to the United States)

Trap-door spiders

Banana spiders (Central America)

Wolf spiders

Orb weavers

Running or gnaphosid spiders

Green lynx spiders

Comb-footed or false black widow spiders

Orange argiopes

Giant crab spiders

Crab spiders



Hunting spiders (Central and South America)

In the South, particularly in the Gulf region, fire ants inflict than-sands of stings each year. Up to 40 percent of the people who live in infested urban areas may be stung each year, and at least 30 deaths have been attributed to these insect bites. The fire ant sting usually produces immediate pain and a red, swollen area, which disappears within 45 minutes. A blister then forms, rupturing in 30 to 70 hours, and the area often becomes infected. In some cases, a red, swollen, itchy patch develops instead of a blister. Anaphylaxis (a life-threatening allergic reaction in which blood pressure falls and the airways close) occurs in less than 1 percent of the people stung by fire ants. Isolated nerves may become inflamed, and seizures may occur.


A bee, wasp, hornet, or fire ant may leave its stinger in the skin. The stinger should be removed by gentle scraping or teasing rather than pulling or tweezing, which can inject additional venom into the body. An ice cube placed over the sting reduces the pain. A cream containing a combination of an antihistamine, an analgesic, and a corticosteroid is often useful. People who are allergic to stings should always carry a kit with antihistamine tablets and a preloaded syringe of epinephrine, which block anaphylactic or allergic reactions.

People who have had a severe allergic reaction to a bee sting may undergo desensitization, which may help prevent such reactions in the future. Desensitization is a process of repeatedly exposing the body to small amounts of the substance that causes an allergic response (allergen) until that response is muted.

Insect Bites

Among the more common biting and some-tunes bloodsucking insects in the United States are sand flies, horseflies, deerflies, mosquitoes, fleas, lice, bedbugs, kissing bugs, and certain water bugs. The bites of these insects may be irritating because of the components of their saliva. The bites cause a variety of reactions, from small bumps to large sores (ulcers) with swelling and pain. The most severe reactions occur in people who are allergic to the bites or who develop an infection after being bitten. For those who are allergic, bites are sometimes fatal.

The insect should be removed quickly. The bite should be cleaned, and an ointment containing a combination of an antihistamine, an analgesic, and a corticosteroid may be applied to relieve itching, pain, and inflammation. People who are allergic to the bite should seek medical attention immediately or use their emergency allergy kit containing antihistamine tablets and a preloaded syringe of epinephrine.

Tick and Mite Bites

Ticks carry many diseases (for example, deer ticks may carry the bacteria that cause Lyme disease) and a few ticks are poisonous. In North America, some species cause tick paralysis, which results in loss of appetite, listlessness, muscle weakness, incoordination, involuntary sideways twitching of the eyes (nystagmus); and a progressive paralysis, moving up from the legs. The muscles that control breathing may also become paralyzed. The bites of pajaroello ticks, which are found in Mexico and the southwestern United States, produce pusfilled blisters that break, leaving open - sores that develop scabs. The area around the sores may be swollen and painful.

Mite infestations are common and are responsible for chiggers (an intensely itchy rash caused by mite larvae under the skin), scabies, and a number of other diseases. The effects on the tissues around the bite vary in severity.


Ticks should be removed as soon as possible. Removal is best accomplished by applying petroleum jelly or some other irritant to the tick or by slowly withdrawing it while twisting it slowly with tweezers. The tick's head, which may not come out with the body, should be removed because it can cause prolonged inflammation or move to deeper tissues.

Tick paralysis may require no treatment, but if breathing is impaired, oxygen therapy or a respirator may be needed. Pajaroello tick bites are cleaned and soaked in a cleansing solution, and dead skin is removed, if necessary. Corticosteroids help reduce inflammation in severe cases. Infections of the sores are common but usually can be cured with an antibiotic ointment.

Mite infestations are treated by applying a cream containing permethrin or a solution of lindane. After treatment with permethrin or lindane. a cream containing a corticosteroid is sometimes used for a few days to reduce the itching until all the mites are gone.

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