As outside temperatures move from the sublime to the ridiculous, more people will be spending time in and around their pools and ponds. Hazards such as drowning are frequently addressed in the media. However, there is another potential danger to people working and playing outside: bites from venomous snakes. A primer on snakes and snake bites will help you avoid being hurt.
Texas is home to many venomous snake species, and approximately 1,000 Texans seek evaluation in the emergency department (ED) annually after sustaining a bite. Some knowledge of where snakes live and how they act can hopefully prevent an undesirable encounter.
This article is not intended to demonize snakes. They are beautiful, fascinating creatures that occupy an important role in the ecosystem. They provide a variety of benefits to humans, including vermin control. Furthermore, some snake venoms are used in the production of human medications. For example, angiotensin-converting enzyme (ACE) inhibitors are derived from venom found in the jararaca, a snake native to South America.
There are many misconceptions about snakes, and even more about snakebites. Sources that one would expect to be reliable, such as the Mayo Clinic and the Centers for Disease Control and Prevention (CDC), continue to provide incorrect or outdated information. The more this misinformation is disseminated, the more difficult it is to educate the public about safely co-existing with these beautiful creatures. The recommendations that follow are evidence-based and come from the most reliable snakebite literature.
Texas is home to 14 types of venomous snakes: 10 rattlesnake species, one cottonmouth species, two copperhead species and the Texas coral snake. Collectively, rattlesnakes, cottonmouths and copperheads are classified as pit vipers, or crotalids. They account for 98% of native snake envenomations nationally. In Texas, approximately 95% of venomous snakebites are attributed to pit vipers, and 5% are caused by the Texas coral snake.
Pit vipers are characterized by large, triangular heads, relatively small eyes, large, retractable and mobile fangs and a thermoreceptor “pit” located halfway between the eye and the nostril. Rattlesnakes will have one or more keratin segments that compose the “rattle” at the distal end. Though some references recommend using the pupil or head shape as a way of distinguishing a pit viper from non-crotalids, it should be noted that both venomous and nonvenomous snakes may have round or elliptical pupils — and pupil shape can change depending on the amount of ambient light. Additionally, many non-venomous snakes can flatten their heads into a triangle shape when they feel threatened. Experts recommend that people learn to recognize the venomous species in their vicinity using multiple characteristics, rather than rely on single features, rhymes or mnemonics.
The Texas coral snake is not a viper. It is a member of the elapid family of snakes that, worldwide, also includes cobras, kraits, mambas and taipans. As a result, people often exaggerate the danger posed by coral snakes.
Let me pre-emptively mention this: There has never been a documented human fatality attributed to a Texas coral snake envenomation. In fact, of the three coral snake species native to the U.S., only the eastern coral snake — which is not found in Texas — has ever caused a human death, and there has only been one fatality in the past 50 years.
Coral snakes are slender with narrow round, black heads. They have round pupils and fixed front fangs. Typically, coral snakes have alternating bands of red, yellow and black. The distinctive coloration has led to several mnemonics that are often used to distinguish coral snakes from non-venomous mimics. “Red on yellow, kill a fellow. Red on black, venom lack” is often true of native coral snakes, but there are multiple aberrant patterns that make reliance solely on the rhyme dangerous. Additionally, some people recite the rhyme incorrectly, placing themselves or others at risk.
There are also non-venomous mimics that have red bands touching yellow bands, such as shovel-nosed snakes. Finally, non-native coral snakes have a variety of patterns and colors that render the mnemonic inaccurate. For everyone’s safety, use of “the rhyme” is discouraged.
Dispel the Myths
Contrary to popular belief, most snakebites occur when the victim is unaware of the snake’s presence. A large study using data from the American College of Medical Toxicology’s North American Snakebite Registry (NASBR) found that only 19% of native snakebites resulted from intentional interaction with the snake. The overwhelming majority occurred when somebody stepped on or near the snake or stuck their hand near the snake. Most bites (55%) affected the lower extremity, particularly in women.
Another common myth is that many snakebite victims are drunk or under the influence of other psychoactive substances. Nothing could be farther from the truth. A study from Dallas found that fewer than 1% of bites involved drug or alcohol use.
Arguably the most common envenomation myth is that baby snakes are unable to control how much venom they deliver per bite, and therefore their bites tend to be more serious than those from adults. This is completely untrue. First, juveniles do have the ability to regulate how much venom they release. Secondly, even if juveniles did not have that control, their total venom volume is much less than that of an adult snake. It is true that in some species the ratio of venom components changes as a snake ages, and some toxins may be more potent in juveniles than adults. However, the total volume of venom delivered is a much more important factor in determining the severity of a bite. That is why, on average, a bite from an adult snake is worse than a bite from a juvenile snake.
Consequences of Snake Bites
The most important thing to remember is that every bite is unique, and a bite from any pit viper of any age has the potential to be mild, moderate, or severe.
More than 85% of pit viper bites will result in envenomation. A “dry” bite, in which no venom is delivered and no symptoms develop, is the exception, not the rule. The most consistent finding in crotalid envenomation is local tissue injury, which is present in more than 95% of cases. Swelling and bruising are usually observed after envenomation and are typically present by the time victims seek medical attention. However, it may take several hours for local findings to appear, and it is imperative to not diagnose a dry bite prematurely.
Blood-filled blisters are common following bites to the finger but may be seen elsewhere on upper extremities and on lower extremity bites.
Systemic toxicity can present in several ways. Nausea, vomiting, fast heart rate (tachycardia) and a sensation of impending doom are nonspecific findings and may represent nothing more than anxiety from being bitten. However, recurrent vomiting may suggest a significant envenomation, and tachycardia may result from fluids leaking out of blood vessels and into tissues. Low blood pressure (hypotension) may also result from fluid shifts or be one manifestation of a severe envenomation.
Abnormal blood-clotting test results are sometimes reported in crotalid envenomation. Fortunately, only a small percentage of patients develop actual bleeding as a result.
Skeletal and respiratory muscle weakness is not typical of crotalid envenomations but may manifest in bites from some rattlesnakes, such as the Mojave rattlesnake.
It is estimated that 30% – 50% of coral snake bites are “dry”, which is likely due to a combination of coral snakes’ relative shyness and their fangs being smaller and less mobile than crotalid fangs.
Pain is often present immediately after a coral snake envenomation, but some clinical features may not manifest for up to 12 hours or more. Unlike in crotalid envenomations, local findings are insignificant following a coral snake envenomation. There may be slight redness, but bruising is absent. Swelling is mild and confined to the bite site; there is no progressive swelling of the affected extremity. Tingling sensations are common and often extremely painful.
How to Avoid Snakes
Prevention is the best medicine, and there are several easy ways to minimize the likelihood of getting snakebitten. In Texas, most bites occur between May and September, although I just treated five bites in the first week of March 2023. Avoid walking barefoot outside during snakebite season, especially at night. Never stick your hand or foot into an area you can’t see. Many hand bites occur when someone reaches under a heavy object, e.g., a large stone. You can also make your home less hospitable to snakes. Keep lawns short and well manicured. Do not allow debris to pile up, because snakes may choose these places to hide.
Some experts recommend using cedar chips to discourage snakes, but the evidence for this is lacking. Do not place mothballs around your yard. These do not work and are toxic to many animal species. They are also illegal in some jurisdictions. Finally, do not waste any time or money on commercial snake repellants. They have proven to be absolutely worthless.
What to Do Post-Bite
If you do sustain a bite, the most important thing to do is remain calm. With proper treatment, most patients fare well and recover fully. Death is, fortunately, especially rare. I authored one of the definitive studies looking at snakebite fatalities. My co-authors and I found that there are an average of 3.4 deaths from snakebite annually in the U.S., and many victims did not seek medical attention. In 2022, a completely preventable death (one of three in the U.S. last year) occurred when someone was bitten while handling a snake at a rattlesnake roundup in Freer, Texas.
If you are bitten, move away from the snake. You do not want yourself or anyone else to incur another snakebite. Do not attempt to catch the snake; doctors do not have to see the snake in order to treat you correctly. A pit viper envenomation is easily distinguished from a coral snake envenomation and from a nonvenomous snakebite clinically. Bringing a snake to the hospital poses risks; even dead and decapitated snakes can envenomate. A gentleman in South Dakota recently died after being bitten by a decapitated prairie rattlesnake.
It is helpful if you can photograph of the snake, but only do this if it can be accomplished quickly and safely. Definitive snake identification is not essential. It certainly should not delay treatment or transport. Unless you are certain that the snake that bit you is nonvenomous, call 911 or arrange for someone to transport you to the ED. In general, it is better to have emergency medical services transport you, unless you are very close to the hospital and someone can get you there quickly. Never drive yourself to the ED.
Remove constrictive clothing and jewelry. Tissue swelling and injury occurs in more than 95% of our native snake envenomations, and anything tight on the affected limb will make the local injury worse. This is why applying tourniquets or constriction bands to the bitten extremity is discouraged.
Position the affected extremity appropriately. Although it was once taught to place the affected limb below heart level, we now understand this is harmful. As previously mentioned, tissue swelling will occur in nearly all crotalid envenomations. Furthermore, for most snakebite victims, local injury will be the only manifestation. Bleeding and systemic toxicity (e.g., difficulty breathing, low blood pressure and refractory vomiting) are much less common. We can minimize tissue injury by elevating the affected limb to 45 – 60 degrees and keeping the elbow or knee straight, not bent. This allows the fluids that have accumulated from the envenomation to drain and reduces the hydrostatic pressures that can contribute to tissue damage.
Coral snake envenomations do not cause tissue damage or significant swelling, so elevation is not essential. I recommend placing the affected limb in whatever position is most comfortable for the patient.
What Not to Do
Knowing what not to do for a snakebite is as important as knowing what to do. Many of the “treatments” that were previously recommended for snakebite have proven to be useless at best and dangerous at worst.
- Do not apply any sort of constriction band or pressure immobilization for pit vipers. It will exacerbate local injury. Furthermore, a study demonstrated that only 5% of people can do this correctly. Multiple toxicology societies issued a position statement discouraging pressure immobilization for our native crotalid bites.
- Do not cut and suck. All this does is make a larger wound and potentially introduces bacteria into the skin.
- Do not apply a tourniquet. There is no benefit in cutting off an extremity’s arterial blood supply unless the patient is bleeding to death.
- Do not use electrical shock treatment. It does not “neutralize the venom,” or whatever nonsense its advocates claim. It causes local injury and could potentially electrocute the victim.
- Do not apply heat. It can damage the affected tissue.
- Do not apply prolonged ice packs. A few minutes at a time is okay (say, 5 minutes on, 10 minutes off) but prolonged cryotherapy is also bad for the tissue.
- Do not use one of those commercially available suction devices. Multiple studies have demonstrated that they do not remove venom and can cause harm.
- Finally, despite many viral social media posts, diphenhydramine (Benadryl) provides absolutely no benefit following snake envenomation.
Snakebites are much less common than many other emergencies, and most physicians get little training on the subject. Get to an appropriate hospital. If you are having life-threatening signs and symptoms (e.g., difficulty breathing, low blood pressure) get to the closest hospital for stabilization. You can get transferred to an expert later. Otherwise, proceed directly to a hospital with a snakebite expert. If you interact with snakes a lot or are outside in snake-endemic areas, you should investigate your regional hospitals to locate one or more specialists.
Space limitations preclude a comprehensive description of what should and should not happen you arrive at the hospital. Just remember a few key points, like elevating the affected limb in crotalid envenomations. This helps with the swelling and the pain, and it does not endanger the patient.
Prophylactic antibiotics should be avoided. The incidence of infection following snakebite in the U.S. is less than 1%. Unnecessary antibiotics increase costs, cause side effects and can contribute to antibiotic resistance.
Acute surgical intervention is inappropriate. Snakebites are medical, not traumatic emergencies. Antivenom is safe and effective, and its use should be considered for all more-than-minimal pit viper envenomations. Even mild bites recover faster when treated with antivenom, and antivenom use decreases the need for pain medication. Because there are two antivenoms approved for all North American pit viper envenomation, it is not necessary to know the exact snake species.
Texas coral snake envenomations frequently cause pain, but objective weakness is rare. Paralysis and respiratory failure do not occur. Coral snake antivenom should only be used when there is any objective weakness on examination.
Remember, snakes are beautiful creatures. They should be respected but not feared. It is easy to safely co-exist with them. Hopefully you will never end up on the wrong side of a snake fang, but if you do, at least now you know what steps to take and what to avoid.