Scott Sandsberry / Yakima Herald-Republic

Two truisms every hiker, hunter and backpacker should know:

1. Even on a long, uphill grind on a 90-degree day, you only think you’re sweating like a pig. Pigs don’t actually sweat.

2. Wherever there are trails, the official state bird should always be the mosquito, closely followed by the biting fly.

There’s not much you can do about No. 1. As for No. 2, you have plenty of options.

DEET: The stink daddy

For decades, DEET was pretty much the only option, despite that it is toxic, feels greasy and invariably finds its way into your eyes as soon as you start to sweat like, well, you know what. Plus, it reeks.

That stink, in fact, is what kept the mosquitoes away in the first place. For years, we were told DEET, like many of the newer insect repellents, worked by confusing or distracting the insects’ olfactory ability, preventing them from picking up the scent of our lactic acid.

Nope. According to a 2008 study at the University of California, Davis, the skeeters are like us: They just think the stuff stinks.

(So do fish, by the way. An angler accidentally getting even the slightest bit of DEET on his fishing line or tackle will actually repel the fish.)

Beyond just the smell, DEET is also really nasty stuff; it can cause neurological damage and can be toxic to the central nervous system. Unless overapplied, though, DEET is relatively benign. According to a 2004 Environmental Protection Agency study, nearly a third of Americans apply it every year, yet reported adverse effects have been few.

That said, those effects can range from minor skin irritations to seizures, delusional behavior and even death. A study at Florida’s Everglades National Park found that a quarter of the park’s employees attributed health effects to DEET that included rashes, burning lips, dizziness, headaches and nausea. At least three people have committed suicide by drinking DEET, and it didn’t take much — less than 2 ounces, and as little as a half-ounce.

DEET also has another drawback: It’s a plasticizer, meaning it will eat away at plastics and polyester. Spray that stuff on your tent and you’ll create a nice hole through which to welcome the rain. Get a DEET-y thumbprint on your sunglasses and, well, you’re buying new ones.

I have an insect-repellent gel that trumpets in large letters the aloe and Vitamin E in its ingredients, but nowhere does it say the word DEET.

Listed in the ingredients, though, is: N,N-diethyl-meta-toluamide.

That — as well the occasional alternate listing as N,N-diethyl-3-methylbenzamide — is DEET.

Picaridin: New kid in town

Picaridin-based repellents have been used in Europe and Australia since the 1990s, but not until 2005 was it approved for use in the U.S. And only since 2008 could U.S. customers purchase repellents with picaridin concentrations of 15 to 20 percent — the only levels at which picaridin can actually rival DEET.

Picaridin doesn’t stink; it doesn’t leave your skin feeling greasy; and it won’t damage your clothes or your tent.

Like DEET, picaridin has been test-proven to be effective not only against mosquitoes, but also biting flies and ticks.

So what’s not to like about picaridin? Well, it doesn’t work that long.

One application is good for maybe three or four hours, while a 50 percent-DEET repellent will give you more than twice that. The answer to that, of course, is simply to reapply the picaridin when the bugs start showing up.

It won’t stink the second time, either.

Permethrin: For your gear

A lot of backpackers and hunters know all about this stuff, and if you don’t, you should.

Permethrin isn’t for putting on your skin; it won’t work that way at all, and besides that, permethrin has nearly as many toxicity issues as DEET. Spray it on your clothing or your pack as directed before going into the field, though, and it’s unrivaled — especially when it comes to keeping off that most unwelcome of hitchhikers. Ticks.

Those cringe-inducing parasites often attach to the fabric of your socks, your pants or your pack. Not only does permethrin prevent that, but it actually kills ticks — much more effectively, studies show, than DEET. That’s one primary reason the U.S. military has been treating combat uniforms with permethrin for more than two decades.

It works for hunters because it’s odorless. It’ll smell pretty ripe when you spray it onto your gear, your tent and your hiking outfit, but once it dries, you’re good to go.

The only negatives are that permethrin products can be pricey and you have to use a lot of it; you might spray on as much as 3 ounces to treat a single shirt. After that, though, that shirt is good for weeks, including multiple wash cycles. Two or three treatments will cover your gear through an entire hiking season.

The natural contenders

If you want to avoid chemical-based stuff, there are plenty of natural oils with varying degrees of effectiveness.

Oil of lemon eucalyptus may be the most effective of these, providing up to six hours of protection. In 2010, Consumer Reports Health ranked lemon eucalyptus alongside several DEET products and picardin as being effective against mosquitoes and deer ticks.

There’s also citronella oil, but applying that directly to the skin may actually increase your heart rate.

The accidental interloper

Hikers have long used Avon Skin So Soft Bath Oil as a mosquito repellent; it was one of those folklore, Grandma-says, home-remedy deals. Avon never marketed the stuff as a repellent nor registered it as such with the EPA, and its effectiveness in dissuading hungry skeeters hasn’t held up well in tests, yet some people continued to swear by it. (Having used it to mixed results, I wasn’t one of those swearing by it.)

The folks at Avon, not being dummies, took advantage of its home-remedy reputation and came out with Skin So Soft Bug Guard, in two primary lines — one with an anti-itch component, in case you get bit by bugs, and one to prevent the bug bites in the first place.

The active ingredient in the latter? Picaridin.

So what do you do?

For my money, your best bet is to treat your hiking clothes and gear fabric with permethrin and then finish off the uncovered skin with a 15 to 20 percent concentration of picaridin. (Repel and Natrapel are two common brands for the latter).

If you don’t like that idea, you can always wear a homemade lei of marigolds, which has a smell mosquitoes don’t like.

Or, then again, you might consider the best natural mosquito repellent ever discovered: catnip oil.

A 2010 study at Iowa State University found catnip oil to be 10 times more effective than DEET. Sadly, it’s also ridiculously pricey. You could easily spend upwards of $20 for a 2-ounce container.

And, you know how cats really like catnip? So do cougars.