Q: Why do cowboys wear long denim jeans out in the heat?
A: Not only does denim look cool and protect legs from the sun and cactus needles, it can actually reduce the venom delivery from a rattlesnake bite. Yes, there’s actually research on this.
Background
If you don’t think snakebites are a big deal anymore, think again. As of 2009 there were an estimated 400,000 to 2 million snakebites globally every year, resulting in 20,000-100,000 deaths and even more disabilities (wide ranges in estimates are the result of different study methodologies as well as underreporting in impoverished areas).
Therefore, reducing snakebite severity is a priority in areas where humans and snakes interact.
Two researchers at Loma Linda University in California sought out to test whether ordinary clothing – in this case, denim – can protect humans from snakebites. The methodology they used to test this is… pretty novel.
The results were published in the journal Injury Prevention in 2009.
Method
I’m guessing that these scientists had a hard time finding human snakebite volunteers, so they had to come up with a different way to test snakebite envenomation.
The research subjects they were able to obtain were 17 southern Pacific rattlesnakes: 8 were small (35- to 54 cm long) and 9 were large (66- to 102 cm long).
To replicate a human limb, the researchers prepared ordinary household latex gloves and filled them with a phosphate-buffered saline solution. These gloves had a unique property – after being bitten, the holes tended to close up, minimizing leakage.
- They could therefore drain each glove and measure the amount of venom that made it into the glove.
- The gloves were also rubbed against human arms so they smelled like humans.
Two gloves were prepared:
Whether the bare glove or the denim glove came first was random.
Snake behavior (including bites) was video recorded so it could be analyzed afterward.
One was a bare, uncovered glove.
The other was loosely covered with a single layer of denim.
Both gloves were suspended with an aluminum hook over the snakes.
Then, a snake was let loose into a small wooden box (they called it an “arena”) and they gave the snake 5 minutes to acclimate to its new environment.
After the 5-minute acclimation period, the glove was presented to the snake. First, the glove was swung around wildly to “harass” the snake, and then it was thrust directly at the snake. Apparently, this is a great way to piss off a snake, because the result was usually a bite.
Each snake got the bare glove and the denim glove, but not one after the other. There were 2 weeks in between the presentations.
After a bite occurred, the glove was quickly transferred to a plastic zip-lock bag, gently swished around to ensure that the venom became equally distributed, and then the liquid from the trial was transferred to a beaker.
- A 10-mL sample was taken from the beaker to a test tube so it could be analyzed.
- The denim samples were also taken for analysis.
If a snake bit multiple times, that trial was discarded.
Results
A total of 31 snakebites were obtained from the glove trials.
There were some differences between the large and small snakes. The large snakes:
- Tended to hang on to the glove longer while biting.
- Injected larger amounts of venom.
But the ultimate results were clear: denim significantly decreased the amount of venom that was injected into the glove.
- The result was 60% less venom for small snakes biting the denim glove, and 66% less venom for large snakes biting the denim glove.
WHY?
- The researchers suggested two possibilities for why denim had the effect it did:
- HOWEVER, analysis of the videos showed that the snakes’ biting behavior was essentially the same between the bare and denim gloves. They waited the same time to strike, they bit roughly the same amount of times, and they hung on to the limb for roughly the same amount of time between the bare and denim gloves.
- There’s evidence for this hypothesis. After analyzing the fabric, the researchers found that much of the venom from the bites ended up in the denim rather than the glove. They measured that 43% of the total venom ended up on the fabric instead of the hand (they also suggested some of the venom ended up ON the hand instead of IN the hand, but they didn’t measure that).
- Additionally, they reasoned that the denim reduced the time the fangs made actual contact with the glove. They figured that once the fangs penetrated the denim, the snakes instinctively began to release the venom without realizing they hadn’t pierced the skin yet.
- Possibly, the snakes chose to react differently to the denim glove than for the bare glove. Snakes can “see” heat, and though the saline solution in the gloves was warm, perhaps the denim covered up the heat and the glove appeared less threatening to the snakes.
- Which leads us to our second hypothesis: The denim itself interfered with the snakebite.
The researchers also determined that denim significantly interfered with the bites of small snakes. In fact, when small snakes bit the denim, 31.3% were dry bites (with no venom at all) vs. 7.7% for the bare glove.
- It seemed that small snakes had a particularly rough time expelling venom into the denim-covered gloves.
CONCLUSION
The results were unmistakable.
If you’re hiking out in the desert, or in a wooded area where there are venomous snakes, you may be tempted to wear shorts to stay cool.
BUT there is scientific evidence that denim jeans are the better choice.
Denim significantly reduced venom delivery from snakebites, and kept smaller snakes from injecting venom at all.
DENIM COULD SAVE YOUR LIFE!
Reference
Herbert, S. S., & Hayes, W. K. (2009). Denim clothing reduces venom expenditure by rattlesnakes striking defensively at model human limbs. Injury Prevention, 54(6), 830-836. Link: https://www.coloradowm.org/pdf/denim.pdf
