The claim: Rumor has it that when applied topically, the liquid laxative mattifies shine, making it a good undermakeup primer for oily skin.
The expert says: Skip it. "Despite its popularity, milk of magnesia is not a good skin treatment," says Howard Sobel, M.D., a dermatologist in New York City. The main ingredients -- magnesium hydroxide and sodium hypochlorite (which is, um, bleach) -- can disrupt skin's delicate acid mantle and pH balance, he says. That can leave skin inflamed and highly irritated.
A better idea: Ulta Professional Matte Prime ($18; ulta.com), which contains skin-smoothing silicones.
The claim: The ingredients in your toothpaste such as baking soda, hydrogen peroxide, and alcohol will dry up a zit -- fast.
The expert says: It'll work in a pinch, but don't make it your main blemish-fighter. "Toothpaste does have a drying effect, but with long-term use, those ingredients can irritate the skin further, causing peeling, redness, and sometimes scarring," Sobel says. Plus, he says there is nothing in your pearly-whites polisher that makes it any more effective than conventional acne treatments.
A better idea: DDF Glycolic 10% Exfoliating Oil Control Gel ($55; ddfskincare.com), which contains both alpha and beta hydroxy acids to clear breakouts.
The claim: The Internet is abuzz with all sorts of beer-base beauty remedies. There are even beer spas across Europe, where people pay money to bathe in the alcoholic beverage. Why? It's said to exfoliate dead skin cells and reduce acne-causing bacteria.
The expert says: It's the real deal. "Most beers contain B vitamins, hops, saccharides, and yeast, which can dissolve dead cells and boost the skin's luminosity," Sobel says. But he also notes that you could get similar benefits from a traditional exfoliating cleanser. You know, in case you don't want your skin to smell like a frat house.
The claim: The same active ingredient that shrinks your hemorrhoids can shrink your undereye bags.
The expert says: It works, but only as a once-in-awhile fix. Undereye bags are usually the result of loose blood vessels and weakened skin, says Sobel. "Phenylephrine, the active ingredient in Preparation H, constricts blood vessels, so it can be effective in reducing puffiness." Just keep in mind: The product isn't intended for cosmetic use, so it's not the best idea to make it your daily eye cream.
The claim: Due to the veggie's high selenium content, adding minced garlic to a clear nail polish will get you longer, stronger (albeit, stinkier) nails.
The expert says: Hold the garlic. "I would not recommend this," says Dana Stern, M.D., a dermatologist in New York City who specializes in nails. "Garlic can cause an allergic contact dermatitis in the surrounding skin, which causes the fingertips to get red and irritated and even develop fissures," she says. "We see this reaction commonly in people who handle or cut fresh garlic, such as chefs or farmers."
A better idea: Sally Hansen Diamond Strength Instant Nail Hardener ($6; drugstore.com), formulated with microdiamonds and titanium.
The claim: The chalky pink stomach remedy is said to clear acne when worn as a facial mask.
The expert says: This is legit. "Pepto Bismol contains bismuth subsalicylate, which could help absorb and suck out oil like a clay mask," says Francesca Fusco, M.D., a dermatologist in New York City. It's also part of the salicylic acid family, which means it helps speed up cell turnover, preventing dead skin cells from clogging pores. One caveat: It can be too dehydrating on some skin types, so skip it if you're on the dry side.
The claim: This tip went mainstream after model Suki Waterhouse admitted to swapping out her shampoo for the sugary soda. She says rinsing with the bubbling beverage gives her hair body and tousled texture.
The expert says: Skip it. "I don't recommend drinking Coca-Cola or pouring it on your hair -- it contains some harsh ingredients," says Devin Toth, a hairstylist at Salon SCK in New York City. It may work, but by drying your hair out, and really, there are far better, less corrosive ways to achieve body and waves, he says.
A better idea: Toth uses Kerastase Densifique Densimorphose Thickening Treatment Mousse ($42; kerastase-usa.com) to boost limp strands.
The claim: Whitening toothpaste can lighten yellow or discolored nails.
The expert says: Go for it! "Nail stains can be lightened with a dilution of hydrogen peroxide," Stern says. Hydrogen peroxide just so happens to be the active ingredient in most whitening toothpastes. Let the paste sit on your nails for 10 minutes. Then gently scrub with a nail brush or toothbrush.
The claim: The headache remedy, all crushed up, can dissolve away flaky dead skin cells.
The expert says: Maybe. Aspirin's chemical makeup is similar to that of salicylic acid, an ingredient often found in dandruff treatments because of its scalp-exfoliating effects. In theory, it should work, "but I do not believe it would do that just by adding it to your shampoo," Fusco says.
A better idea: Add a tablespoon of sugar to your regular shampoo. As you scrub, the granules mechanically exfoliate your scalp, then dissolve away, Fusco says.
The claim: Going to sleep with tape over wrinkle-prone areas -- like a furrowed brow -- will relax lines over time.
The expert says: Skip it. "Adhesive tape will not stop facial muscles from moving like Botox does," Sobel says. Plus, the adhesive material on the tape can irritate and tear skin, clog pores, and cause an allergic reaction, he says.
A better idea: L'Oreal Revitalift Daily Volumizing Concentrated Serum ($24; lorealparisusa.com), which contains hyaluronic acid to fill wrinkles from the inside out.
The claim: Aerosol nonstick cooking spray sets and dries your mani in seconds.
The expert says: Spritz it! Most quick-dry nail products contain solvents that speed up drying time without dissolving your nail polish -- typically silicones, Stern says. Pam brand contains a form of silicone, which is likely what's doing the drying.