Between the West Nile virus that mosquitoes carry and Lyme disease from ticks, insect repellents are becoming a bulwark against disease.
This year, West Nile has made an early appearance. The first detection of the virus in a mosquito was in Greene County on May 17 - the earliest since testing began in 2000.
In 2010, Pennsylvania had 28 reported human cases, the most since 2003. New Jersey had 29 cases. Older people tend to be the most at risk.
In the case of the biting flies, you could almost say using insect repellent is a mental health aid.
But while slathering chemicals on your skin is a good way to keep the bugs at bay, what is it doing otherwise?
It's the same debate that arises in other domains, such as cleaning supplies: Are the products that actually work also not so good for you? And are the ones that are ostensibly safer not as effective?
"With some cosmetics, we say these are unnecessary chemicals and you can avoid them," said Sonya Lunder, senior analyst with the Environmental Working Group, a national nonprofit that is concerned about people's "body burden" of potentialy harmful chemicals.
But it's a different story with things like sunscreens and insect repellents, which often are a necessary part of being outdoors.
On its West Nile information Web page, the Centers for Disease Control and Prevention said two repellents have "demonstrated a higher degree of efficacy in the peer-reviewed, scientific literature" - DEET and Picaridin.
DEET is a broad-spectrum repellent used worldwide since 1957. The higher percentage of DEET a product has, the longer it works.
But it's serious stuff.
Some who use DEET, especially at high concentrations, have skin reactions. The New York state health department notes on its website that its use - mostly, ingesting it - has been associated with rare reports of slurred speech and confusion as well as seizures.
When it comes to children, the anxiety amplifies. They have more skin relative to the size of their bodies, and they have sensitive developing systems. Plus, they often get the stuff on their hands, which they then stick in their mouths.
The CDC and the American Academy of Pediatrics recommend not using DEET on infants under 2 months old.
Health Canada, the CDC's Canadian counterpart, goes further, saying that prolonged use should be avoided in children under age 12, with more specific recommendations for other age groups.
Picaridin, said to be less irritating to the skin, entered the U.S. market in 2005.
Another alternative is oil of lemon eucalyptus, but the CDC notes that the label says it should not be used at all on children under 3 years.
Then there's citronella and even, of all things, soybean oil, which Lunder says studies have shown is actually pretty effective.
But critics note that some of these alternatives are not vetted as thoroughly by health officials because the ingredients are "natural" instead of synthetic.
Whatever you use, the CDC warns against applying repellent to cuts, wounds or irritated skin.
Wash your hands after applying repellent.
Lunder has a friend whose child put on insect repellent, grabbed a pear, ate it and not long afterward, threw up.
"People don't understand or respect how potent these chemicals can be," Lunder said.
If it's a spray, don't use it in enclosed areas. Don't spray it in your face. Just as you don't want to eat this stuff, neither do you want to inhale it.
Use it only as often as you need to. Wash treated skin with soap once you no longer need the repellent's protection.
The CDC also recommends against using combo products of repellent and sunscreen. Lunder agrees. They're for different things and are often needed at different times of the day.
If you wind up using both products at once, apply the sunscreen first, then the repellent. Sunscreen has penetration enhancers, Lunder says, and you may not want that effect with the repellent.
The good news is that scientists are learning a lot more about why insects do - or don't - bite. They've dedicated intensive research into mosquito olfactory organs and plumbed the intricate realm of odor recognition.
Yup, they bite us because we smell good to them, in essence.
Last month, a Vanderbilt University professor of pharmacology reported the discovery of a new class of insect repellent that, instead of changing your smell, disrupts the mosquito's sense of smell.
The researchers said it could work on all types of insects.
Whether it could ever become part of a commercial product and make it through the approval process makes it hardly worth waiting for, but how nice that progress is being made.
Meanwhile, if you don't like any of this, at least wear long sleeves and long pants.
GreenSpace: Information on Insect Repellents
Environmental Protection Agency:
Centers for Disease Control and Prevention: www.cdc.gov/ncidod/ dvbid/westnile/repellentupdates. htm
American Academy of Pediatrics:
Health Canada: www.hc-sc.gc.ca/ hl-vs/iyh-vsv/life-vie/insect-eng.php
Contact staff writer Sandy Bauers at 215-854-5147 or firstname.lastname@example.org. She blogs at http://go.philly.com/greenspace.