It is high summer, when the buzzing of insects serves as the soundtrack to the season. Chemical repellents have long been considered the best way to ward off mosquitoes and ticks, but many swear by foods and other deterrents rumored to be less toxic.

But do these work? One expert, Stephen Gluckman, professor of medicine at the Perelman School of Medicine at the University of Pennsylvania, and a specialist in infectious diseases, explains the myth of garlic and the gold standard in bug-bite prevention.

By the Numbers:

The most comprehensive comparative study, Dr. Gluckman says, was published in the New England Journal of Medicine in 2002. Volunteers applied 16 products marketed as bug deterrents to an arm, then placed that arm in a cage filled with mosquitoes. The best product was one with 24% diethyltoluamide, also known as DEET.

"That protected the volunteers for 301 minutes," Dr. Gluckman says. Other products had some effect, but not nearly as marked. The best product containing citronella oil, which has been marketed as the "mosquito plant" and is classified by the Environmental Protection Agency as a biopesticide, protected volunteers for 20 minutes.

While many consumers worry about the toxic side effects of DEET, Dr. Gluckman says, "There has never been one credible study showing a side effect from DEET other than an allergic reaction."

It is possible that consumers confuse DEET with the toxic pesticide commonly known as DDT, which has been banned in most countries. People who are worried about DEET, he says, "are missing the point, since bites from ticks or mosquitoes aren't only uncomfortable but also carry the risk of transmitting serious viruses and bacteria like the ones that cause West Nile or Lyme disease."

Before You Eat This:

For millennia, people have used certain foods and herbs to combat bug bites or to scare insects away. Garlic has been one of the most popular foods used, but Dr. Gluckman says every related study he has seen has shown no greater effect than when subjects ate a placebo.

Some people swear by certain types of vitamin B, including thiamine (B1), an excess of which is excreted through the skin and is said to repel mosquitoes. However, "there is no evidence that ingesting thiamine works at all," Dr. Gluckman says. Same goes for eating bananas, and for any number of products that claim to deter bugs through ingestion. "As a general rule,"he says, "if the Centers for Disease Control and Prevention doesn't mention that something is an effective bug repellent on its website, it doesn't work."

On the flip side, eating spicy foods or drinking alcohol may cause a person to breathe more heavily, and since mosquitoes are attracted to the carbon dioxide we exhale, the more labored the breath is, the more likely that person is to be the target of insects.Scratching the Itch

If a person suffers from severe allergic reactions to mosquito bites, there aren't many nonchemical ways to treat the itching and swelling. Foods high in vitamin C are known to combat inflammation, though Dr. Gluckman is skeptical that eating loads of oranges will lessen the swelling from a bite, since vitamin C doesn't impact histamines, chemicals that trigger the immune system.

That said, Dr. Gluckman says, a chemical histamine blocker such as Benadryl or Zantac works best. "If you don't want to put it in your body, there are topical versions of Benadryl," he adds.

Prevention Techniques:

The best way to keep the bugs away is to discourage their presence, Dr. Gluckman says. Drain any standing water in your backyard. Try to catch and kill mosquitoes early in the season, before they breed, by using a carbon-dioxide trap.

Wear tightly woven fabrics, since mosquitoes can easily bite through a cotton T-shirt. Dr. Gluckman soaks his hiking clothes in permethrin, a synthetic chemical that deters bugs but doesn't get absorbed into the skin.