The spray of a skunk is not only incredibly stinky—it's also notoriously difficult to get rid of. An old folk remedy is to bathe in tomato juice, but tests show that only masks the odor. In this Science Update, you'll hear about a better way to neutralize the stink.
Why skunk stink sticks around. I'm Bob Hirshon and this is Science Update.
A listener from Maine, who prefers to remain anonymous, wrote to say that his dog got sprayed by a skunk, and that the smell has infiltrated his clothes and his entire house. He's eager to know what he can do to enter polite society again.
We consulted chemist William Wood, of Humboldt State University in California. He says skunk spray contains smelly sulfur compounds called thiols, which our nose can detect in tiny concentrations.
And it will stick to things like hair and wool and various paint around the walls, and it will dissolve in there and slowly come out.
He says a pet dog can be bathed with a homemade concoction that chemically neutralizes the thiols.
You can wash it with a mixture of three percent hydrogen peroxide and a quarter cup of baking soda per quart of hydrogen peroxide. And a little liquid detergent.
Clothes and other objects can be washed with a bleach solution. But if the smell has drifted all over your house, Wood says all you can do is air it out.
If you've got a science question, don't raise a stink. Call us at 1-800-WHY-ISIT. If we use your question on the show you'll get a free Science Update mug. I'm Bob Hirshon for AAAS, the Science Society.
Making Sense of the Research
It's obvious that some smells are stronger than others. But why? As it turns out, the key lies not only in the nature of the odor itself, but also in our ability to detect it.
Thiols, the compounds that make skunk odor so... er, distinctive, are chemicals to which our noses are super-sensitive. We can detect thiols at the level of parts per billion. In other words, if thiols make up just a few billionths of the volume of air and other gases in a room, we can smell them.
As for the foul quality of the smell, that's largely due to the sulfur in the thiols. Sulfur is a key component of many other obnoxious smells, like rotten eggs or human flatulence. Another kind of sulfur thiol is actually added to natural gas (which is itself odorless) so we can easily smell a gas leak.
Skunk spray also contains chemical compounds called thioacetates, which decompose very slowly into (guess what?) thiols. So not only are you hit with an initial blast of thiols, but you get a slow release of thiols from the thioacetates for a long time to come. That's why the smell of skunk tends to linger for so long.
You may have heard that tomato juice gets out skunk spray. But according to Wood, that's an illusion. He explains that skunk odor is so powerful, and binds so tightly to the odor receptors in your nose, that after a while you stop smelling it as strongly. Your receptors get tired out: in fact, it's called "olfactory fatigue." If you've ever been in a kitchen cooking smelly food, you may have noticed that you get used to the smell after a while. But if you leave the room for fifteen minutes and then come back, the smell is overpowering.
The same thing happens when you use tomato juice on skunk spray. Tomato juice also has a strong smell, so at first your nose reacts more to the new tomato juice smell than to the old skunk smell. But after a while, the effect wears off, and you're back to smelling like skunk (or skunk parmagiana).
The hydrogen peroxide and baking soda recipe that Wood suggests (invented by Illinois chemist Paul Krebaum) works better because it actually changes the chemistry of the skunk spray. It converts the smelly compounds into odorless chemicals. But the drawback is that you have to apply it to a surface; for skunk smell in the air, the best solution is to open a window.
Now try and answer these questions:
- Why is the smell of skunk so powerful and hard to remove?
- What is the difference between thiols and thioacetates? What roles do they play in skunk odor?
- How does treating skunk spray with tomato juice differ from using the hydrogen peroxide solution?
- Suppose two different people, John and Jane, are in the same area that has been sprayed by a skunk. John notices the skunk odor much more than Jane does. What are some possible explanations for this?