Whether we are repelled by skunk spray because of its irritancy, because of a cultural construct, or because of an evolutionary predisposition, the annoying quotient doesn’t change much. It’s annoying no matter why it’s annoying, and part of that is our sensitivity to these chemicals. Our noses can detect skunk spray at relatively low levels—about ten molecules per billion.
It’s not quite clear why we’re able to detect thiols in such low doses. One theory has to do with how the thiols bond with the receptors in our noses. Block says, “There’s no reason why a very low level of a sulfur compound should fit particularly better in an enzyme cavity if you use the old-fashioned lock and key model for enzymes and substrates. There’s no simple explanation for the detection of thiols at extraordinarily low levels, unless you invoke some sort of process where chemically the binding should be extremely good.” One idea is that metals aid in the olfactory binding: “metals, such as copper, do bind with sulfur very, very well,” says Block. “Is it simply a coincidence that a particularly foul-smelling component in skunk spray, 2-quinolinethiol, is also known to strongly bind to metals?” Block asks. Metals in our olfactory receptors could act like glue, helping the molecules attach more securely to the receptors.
There is no question that once those molecules are lodged in a receptor, they’re hard to get out. This leads to olfactory fatigue. The receptors in your nose tire of sending signals. The neurons stop firing, and the brain takes that to mean the odor is gone. This is why tomato juice is thought to work as a skunk spray remedy, says chemist Paul Krebaum. “There’s nothing in tomato juice that takes the smell away. It’s a total myth. What happens to most people—by the time they’re done washing their pets in tomato juice—is that they’ve been exposed to the skunk spray for so long that they’ve developed olfactory fatigue.” Meanwhile, the tomato juice locks into other receptors, causing them to fire. The skunk smell is masked by the tomato smell.
Although tomato juice won’t do the trick, there is something that will. “I was working on a project where we were etching grains of zinc sulfide with acid, and it was producing hydrogen sulfide gas as the by-product,” says Paul Krebaum. It stank. People started to complain. “I needed a way of absorbing this hydrogen waste product as it was being generated.” The solution was a chemical reaction: alkaline hydrogen peroxide transformed those stinky molecules into something else. After his colleague’s cat had a run-in with a skunk, Krebaum wondered whether his remedy might work on the skunk spray, too, because the thiol molecules are shaped like those of hydrogen sulfide. “So I made up a milder version for him,” Krebaum says, and it worked. Recognizing the utility of the discovery, Krebaum wrote to Chemical and Engineering News and the remedy was published in an article titled “Lab Method Deodorizes a Skunk-Afflicted Pet.”{22} The story got picked up by the Chicago Tribune, and the rest is history. Now the recipe is available on Krebaum’s Web site.{23}
Here’s how it works: Mix 3 percent hydrogen peroxide with soap and baking soda, apply it to your skunked pet, and rinse. It works by a process called oxidation. The hydrogen peroxide reacts with the thiol to produce a disulfide, which is much less smelly. If the reaction continues, the disulfide turns into sulfonic acid with the addition of more oxygen to the sulfur group of the thiol. Block also uses oxidizing agents for odor elimination in his lab.[1] “We use this in the laboratory because we work with a lot of thiols, and you can’t even flush things down the drain without causing mischief elsewhere in the building because the drains have vents and so forth. You could use peroxide, but bleach is much more effective. Now bleach is not a good remedy for a pet, nor would you want to use concentrated hydrogen peroxide. But a 3 percent concentration is safe.” (Despite the peroxide, Krebaum hasn’t gotten many complaints of fur bleaching.)
Krebaum’s recipe also includes soap, to get the greasy spray off the pet, and baking soda, which he says neutralizes the sulfonic acid and helps convert another stinky component in the spray into something more benign. Thioacetates are thiols with acetic acid attached. “The stinkiest sulfur compounds always have a free hydrogen on the sulfur and some number of carbons on the other side. If you remove that hydrogen and attach acetic acid to it, it’s kind of a temporary attachment because it will break down with water to form a thiol,” Krebaum says. That’s why if a dog gets wet, it will start to stink of skunk again, months after the initial spraying—the thioacetates hydrolyze into thiols, and the smell returns. These chemicals “act to give the skunk spray long-lasting coverage,” says Krebaum. The baking soda raises the pH, which helps speed up the breakdown of thioacetate into acetate and thiols, which can then be oxidized.
This is a rare success story, in which the offending annoyance can be effectively treated. The $3 elixir neutralizes the annoyance on contact, turning it into something benign.
5. Bugged by Bugs: An Epic Bugging
One of our colleagues, NPR science correspondent Christopher Joyce, told us about what annoys him, and he thinks he has it worse than anyone. It’s not that his pet peeve is more unpredictable, longer lasting, or more unpleasant than other people’s. It’s just that he’s annoyed at a time when he should have some respite from being annoyed. He’s annoyed while he sleeps.
You can be annoyed all day long, but you can go to bed at night knowing that except for a noisy neighbor or his dog or a mosquito in the air or a lumpy bed, you’ve escaped the daily mine field of annoyance. Not me.
No, when I go to bed, I enter the annoyed man’s nightmare—the recurring dream. The details change, but the theme is always the same. I’m trying to get somewhere important. I’m trying to catch a plane, and time is running out. Trying to get to a meeting or a class on time. Trying to find a bathroom, urgently, of course. Worst of all, trying to rendezvous with a beautiful woman. Oh, yes, that’s when it’s most annoying.
Because what happens, every time, is that something keeps me from getting there. I’m driving, and I get lost. My cabdriver stops to get lunch and disappears. There’s an accident on the freeway. The public toilets are under repair and out of service. Once there was an earthquake, and I had to get out of a car and walk (I think that was a woman-rendezvous dream).
At first, I struggle diligently to find an alternate route—after all, I’m a responsible person, at least in my dreams. I hail down another cab, book another flight. But soon enough it dawns on me that whatever I do is hopeless. I am foiled, again and again. Sorry, flight canceled due to bad weather. Road work ahead. Bridge down. Detour.
Now, I’ve traveled a lot in my life, all over the place, in war zones and Amazonian rainforests and Tibetan highlands and on rickshaws and in dugout canoes. I know about washed-out bridges and drunken bus drivers and chain-smoking customs agents who’ll wait days until you come up with the bribe. My subconscious is loaded with examples with which to impale a traveler like a butterfly pinned to a patch of felt.
Eventually, I reach a stage of weary acceptance. I’m not going to make it to my destination. I realize I’m in that dream again, I’m asleep, and that bastard who lives somewhere in my head is doing this on purpose, writing the script as I sleep, making sure that whatever clever solution I come up with, he’ll trump it. And there’s nothing I can do because that bastard is me… the annoying me, annoying me.
1
Just like William Wood, Eric Block’s research in garlic chemistry had colleagues downwind from his fume hood flaring their nostrils. “I was contacted by our president’s office about a strong pizza smell in his office. The solution was to invest several million dollars in new fume stacks to transport the fume hood exhaust gases higher up in the atmosphere away from campus offices!”