"Who knew?" use: Clears up pimples
How it works: Pastes that contain baking soda and hydrogen peroxide (most brands make a product with these ingredients) fight blemishes in two ways: by killing bacteria and by drying and exfoliating the skin. Toothpaste isn't as effective as over-the-counter spot treatments, notes Dr. Debra Jaliman, author of Skin Rules: Trade Secrets from a Top New York Dermatologist ($23;amazon.com)." But if you don't have acne medicine on hand, she suggests dabbing on a bit before you go to bed.
FYI: Skip this remedy if you've got sensitive skin. Toothpaste is harsher on the skin than drugstore pimple gels and creams and could cause your blemish to become more inflamed.
"Who knew?" uses: Treats insect bites and stings, fights dandruff
How it works: Attacked by mosquitoes? Crush two aspirin and make a paste with water. The drug's pain-relieving ingredient, acetylsalicylic acid, is an anti-inflammatory, so it should work the same way on skin as on inflamed joints, Zeichner said. Got a flaky scalp? Salicylic acid is also a superstar exfoliant. Mix the paste with your regular shampoo, rub it into your scalp and leave it on for a few minutes, then rinse.
FYI: Salicylic acid occasionally causes skin irritation. If you experience a burning sensation, wash it off right away.
"Who knew?" use: Kills lice.
How it works: No one knows exactly why this brand of mouthwash is so deadly to the creepy critters that nest in our hair. But Graedon credits "some combination of alcohol and essential oils." The treatment is simple: Douse hair and scalp with Listerine (the original amber formula), let it soak for about 10 to 15 minutes, then rinse.
"We keep hearing that Listerine works when standard over-the-counter lice shampoos and conditioners fail," Graedon said.
FYI: Don't try this if you have open sores on your scalp or hands; the alcohol in the mouthwash could sting.
"Who knew?" uses: Shrinks under-eye bags, buffs up muscles
How it works: The ointment contains the vasoconstrictor phenylephrine, which shrinks swollen hemorrhoids. But Preparation H can also reduce the puffy signs of too-little sleep when applied under the eyes, said Dr. Joshua Zeichner, assistant professor of dermatology at the Icahn School of Medicine at Mount Sinai in New York City. And that's not the product's only beauty trick. For a big night out, exercise physiologist and physical therapist Scott Weiss suggests spreading a thin layer on your arms and legs to add insta-definition. The phenylephrine temporarily tightens skin so it clings more firmly to muscles.
FYI: Stick to the regular ointment, Zeichner said. The cooling gel contains witch hazel, a potential irritant, while the anti-itch variety has hydrocortisone, which can thin skin over time.
"Who knew?" uses: Relieves muscle soreness and headaches, cures nail fungus
How it works: The cough remedy's famous minty scent comes from menthol, which acts as a topical analgesic for cold-induced body aches. But Weiss and his clients like to massage it into sore muscles after tough sweat sessions. "The massaging and ointment work in tandem to increase blood flow to the area," he says. Menthol has even been shown to ease migraine pain: A 2010 study found that a menthol solution applied to the forehead and temples reduced symptoms. Several other ingredients—including thymol, camphor and eucalyptus oil—have anti-fungal properties.
"I've been recommending VapoRub as a safe, easy way to get rid of nail fungus for years," Graedon said. "You coat the nail once or twice a day."
FYI: Certain over-the-counter topical pain relievers that contain menthol have been reported to cause chemical burns. Most of those products have a much higher concentration of the compound than Vicks. But if you notice pain and/or blistering, stop using the rub and see a doc.
"Who knew?" uses: Gets you to sleep, controls nausea
How it works: This allergy medication's active ingredient, diphenhydramine, is an antihistamine, which means it inhibits the action of neurotransmitters called histamines that can trigger symptoms like sneezing and itching. But histamines also play a role in regulating the body's circadian rhythms, helping to keep you alert during the day. So when your histamine levels drop, you start to feel sleepy. Charles Rocamboli, DO, an emergency physician in Los Angeles, has found that a dose of Benadryl works wonders for ER patients who are struggling to get some rest: "They end up sleeping for hours," he said. Benadryl also interferes with the histamines that deliver nausea signals to the brain—which explains why it's often recommended for motion sickness and morning sickness.
FYI: The drug is not a long-term fix for insomnia. Your body can quickly build up tolerance, so the longer you take it, the less likely it will help you sleep. It also tends to have a hangover effect and may impair driving.
"Who knew?" use: Soothes cracked lips
How it works: The topical steroid, applied two or three times a day, can reduce inflammation in severely chapped lips, "making it easier for splits and cracks to heal," Zeichner said. It's also moisturizing, thanks to its petroleum jelly base.
FYI: Apply the ointment only to the outer, dry part of the lip, rather than the inner, wet lip, Zeichner said. (You want to avoid contact with the inside of the mouth.) Make sure you're using ointment and not a cream, which contains potentially irritating preservatives. And don't use it for more than two weeks. Not seeing improvement? Time to go from DIY to the derm.