Rattlesnake Vaccines, Benadryl®, and Other Snake Nonsense
What Facebook needs is a vaccine for viral misinformation.
Being a wildlife educator has its ups and downs. When you help someone get past their “only good snake is a dead snake” thinking and they start letting wildlife go in peace, that is a win worth celebrating. However, some days it feels like the wins are drowned out by the thousands of others just waiting to jump on the latest viral bandwagon.
I get it, though. We all like learning something new, and when we think we’ve stumbled across what seems like a life-saving tip, we want to share that with others. Well, brace yourself for another potentially life-saving tip:
Not all of the random posts in your feed are reliable.
Two of the more annoying “tips” floating around are that you should give your dog Benadryl® for snakebite and make sure to request a rattlesnake vaccine from your vet. These sound like important tips to share, but does the science support these claims?
A large study on the subject says no. This study primarily focused on the efficacy of F(ab′)2 antivenom but also investigated whether vaccines or antihistamines provided any benefit. After examining 272 cases of rattlesnake envenomations, a clear conclusion was issued.
“In dogs with rattlesnake envenomation, there is no evidence that use of glucocorticoids, diphenhydramine, prophylactic antibiotics, or vaccination lessen morbidity or mortality.”
Have a look at the study for yourself, if you are skeptical.
Let’s put that in list form for emphasis.
- Neither glucocorticoids (a class of common steroid anti-inflammatories) nor diphenhydramine (e.g. Benadryl®) showed any benefit in the treatment of snakebite.
- Proactively treating with antibiotics shows no benefit for snakebites.
- Rattlesnake vaccines have not been proven to lessen the duration or severity of envenomations.
Do some vets offer these treatments? Sure. This is largely because most veterinarians are not toxicologists. The reason your family physician refers you to the ER or a specialist is that certain medical emergencies (like snakebite) require special knowledge and tools. Poison Control Centers exist because toxicology is not a topic most doctors specialize in.
The same is true for veterinary doctors. Many try to treat envenomations the best that they know how, even if it is not their area of expertise. Most of these pets survive because most envenomations are sublethal, but that is not proof that the treatment provided was proper.
Another big reason why you might hear a vet recommend diphenhydramine is that most people are either unable or unwilling to bear the cost of proper snakebite treatment. Antivenom is not cheap, so relatively few people will pay for it and relatively few vets stock it. Lacking the option of providing the proper serum, vets are often left with what equates to putting a Bandaid on a bullet wound. Again, this does not make the treatment proper or useful; it’s just an attempt to make do with the available options.
The same goes for the rattlesnake vaccine. There is no clear evidence that the vaccine provides any benefit for dogs, but many vets offer it on the theory that “it might do something.” Remember, we establish whether a treatment works through scientific testing and studies. The simple fact that a product gets produced, sold, and administered does not mean it provides any benefits.
Why don’t these treatments work?
Some of you may need more explanation than just “the science doesn’t support it.” With so many viral posts and every tenth person on the internet waiting in the corner to jump out and shout “Benadryl!! Benadryl!!” anytime a dog is bitten, it might feel like there has to be something to these treatments. Let’s examine that a moment.
Benadryl® is an antihistamine. Its primary use is as an inverse agonist of the histamine H1 receptor. When used properly, it is a great drug with many applications from treating allergies to acting as a sleep aid. For all its uses, though, it is not an antivenom. You will not find “snakebite” anywhere on the label under recommended applications.
While it is possible (extremely rare, but possible) to be allergic to snake venom, rattlesnakes and other venomous snakes did not evolve to produce allergic reactions in their prey. Depending on the species, snake venom can work to destroy cells, attack blood vessels, inhibit the nervous system, damage heart muscle, or other adverse effects. These are examples of venom doing what it is supposed to do, which is to subdue prey.
Put simply, antihistamines are not the treatment for snakebite because cell death is not an allergic reaction.
Swelling and edema from snakebite are not a result of excess histamine, they are the result of the venom. Even if you manage to mask some of the symptoms with over-the-counter medications, that does not stop the damage from taking place. Antibodies are what fight foreign organic proteins, histamine activity is a side issue. A doctor may also use antihistamines or corticosteroids in a hospital setting (for example, if someone is known to be allergic to antivenom or has a latex allergy), but they are not the go-to medicine for treatment. Antivenom is the definitive treatment for snakebite.
Rattlesnake Vaccines
A rattlesnake vaccine sounds like a great idea. However, it is pretty easy to understand why science hasn’t proven this out yet.
The way a vaccine works is by giving your body’s immune system a head start on a virus or other microorganism. For example, if you are exposed to measles but have never encountered a Morbillivirus virus before, the pathogen can multiply quickly and overwhelm your immune response. A vaccine introduces an inert strain of the organism ahead of time to train your body to fight back. This usually results in your body being able to go into action faster and destroy the virus before it becomes entrenched.
That is a very different mechanism than an envenomation.
When you encounter a virus, we’re talking about an organism that is literally too small to see with the naked eye. Venoms are delivered in vastly larger quantities by comparison. A virus’s main job is to reproduce. Venoms act immediately and do not increase in volume.
Venoms do not embark on a microscopic race with your antibodies to see who can reproduce faster. They go to work, en masse and right away, on whatever types of cells they act upon. Yes, your body begins to fight this invader with antibodies as quickly as it can, but if there is a benefit to a vaccine, practical studies have not been able to detect it. This is why a similarly large volume of antivenom is often required for treatment.
One last bit of nonsense…
Since we’re on the topic of snakebite, let’s address bites from nonvenomous snakes for a moment. Wildlife educators routinely refer to these snakes as “harmless.” There are even a few snakes that are technically venomous, meaning they do produce compounds that help them subdue their small prey but that are not a threat to humans. Almost invariably, someone chimes in with “but it can still bite you and give you a nasty infection.”
Let’s be clear: snakes do not have some weird, especially-dangerous bacterial cultures in their mouths.
A bite from a dog, cat, or even a human is much higher-risk than a bite from a nonvenomous snake. Sure, any break in the skin has the potential for infection because germs are on your skin and around you all the time. Regardless, a bite from 80% of the world’s snakes is medically akin to a papercut.
Some people have been prescribed antibiotics after receiving a bite from harmless snakes. Prophylactic (preventative) antibiotics are a bad idea for snakebite for the same reason they are a bad idea in other settings. They get prescribed because people generally expect their doctor to “do something” in order to get paid, but all this does is breed resistant super-bugs. In fact, antibiotics are rarely warranted even for venomous snakebites (usually in the setting of necrosis for extreme cases).
It is true that doctors may want someone with a compromised immune system to take antibiotics after any laceration, but that is not unique to snakes. A doctor may also suggest a tetanus shot if you receive any animal bite. Whether or not snakes present any unusual risk in that regard, it never hurts to make sure your boosters are current.
To be fair, there are some tropical snakes with substantial teeth that can inflict deeper cuts (such as the Green Tree Python). The problem there is not a bacterial load but rather mechanical injury. At any rate, the majority of people in the world do not live near those snakes. Ratsnakes, watersnakes, and almost any snake you might run across falls squarely within the realm of perfectly harmless.
The conclusion here is that proper snakebite treatment is poorly understood by most human and veterinary doctors. If you or your pet suffers a snakebite, you should really focus on getting to a doctor that specializes in and has ample experience treating these injuries.
What you should NOT do under ANY circumstances is get your medical advice from random viral threads on social media.
I hope this helps to clear things up!
For more published evidence recommending that antibiotics should generally not be used for North American snakebite, read this poster or this study.
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You can also download my book, A Primer on Reptiles & Amphibians: A Collection of Educational Nature Bulletins, for free from my website.
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