As the world has grown smaller, more and more foreign-made goods are hitting our shores. Among them, a flood of fakes, fueled in part by the Internet and the ease with which we can buy products directly. Last year, U.S. law enforcement agencies—including U.S. Immigration and Customs Enforcement’s Homeland Security Investigations—shut down 29,684 websites that were illegally selling counterfeit goods online.

Buying counterfeit goods—whether online or in person—comes with a big risk. Not only do fakes cost U.S. businesses as much as $250 billion in lost trade annually, but many are also downright dangerous. Here, some of the latest to watch for:

Read our special report, "Made in America," check our coverage of the best American-made appliances, and find out what makes a car American.

Many consumers know to look for the UL label, the safety seal that the independent Underwriters Laboratories puts on more than 22 billion products annually. Fraudsters create knockoff labels for appliances and electronics, particularly low-cost items such as power strips and extension cords as well as mobile-phone chargers and batteries, says UL’s consumer safety director, John Drengenberg. Manufacturing shortcuts on products with counterfeit UL labels could lead to fire and shock hazards, among other dangers. Some extension cords with fake labels, for example, have been found with copper wiring that’s inadequate to carry the appropriate current.

Toasters

In April 2013, customs officers intercepted 15,000 fake toasters smuggled into a Los Angeles-area seaport from China. They had the fake UL labels shown above left. (One hint: the misspelling in “ONE YEAN WARRANTY.”) As a deterrent, UL has redesigned its markin the form of a gold hologram with embedded codes and color-shifting ink, such as you’ll find on high-denomination U.S. currency.

Counterfeit small appliances can be deadly. The Consumer Product Safety Commission (CPSC) has warned people for years about products that lack a ground-fault circuit interrupter (GFCI), which protects against electrical shock.

Hair dryers

Like most fake hair dryers, the one shown was missing a GFCI, which can prevent electrocution if the dryer falls in water. The CPSC advises consumers to look for a large, rectangular-shaped plug at the end of the dryer cord indicating the presence of a GFCI, and certification from a recognized testing laboratory like UL on the dryer or its package.

Illicit aftermarket auto parts are showing up at an alarming rate, says Bruce Foucart, director of the National Intellectual Property Rights Coordination Center, led by U.S. Immigration and Customs Enforcement. The parts are usually smuggled into the U.S. and bought by independent stores—sometimes knowingly, sometimes not. “At best, these parts will not perform as well as authentic ones,” Foucart says. “At worst, they can fail catastrophically, with potentially fatal consequences.” Most vehicle components can be faked.

As a general rule, consumers are best off buying auto parts from authorized dealers and retailers.If you shop elsewhere, make sure that you inspect the packaging carefully for the correct brand name, logo, and graphics. Andbe wary of subtle differences in artwork, colors, fonts, and spel-ling (for instance, “AZDelco” instead of “ACDelco”). Amazingly low prices should send up ared flag, too.

Airbags

The National Highway Traffic Safety Administration (NHTSA) says that counterfeit airbags are sold as replacement parts for vehicles that have been in a crash. They look almost identical to original equipment, including bearing the brands of major automakers—but NHTSA testing found that fakes consistently malfunctioned. Some didn’t deploy, and others expelled metal shrapnel during deployment. In 2014, a Canadian man was sentenced to six months in prison for selling more than $33,000 worth of fake BMW, Toyota, and Honda airbags (shown above). They were sourced from China and sold on eBay for about a year, according to U.S. officials. Court records show that in follow-up testing, a bag failed to deploy as designed and shot flames from the top and bottom.

Brake pads

Avoid the temptation to save a few bucks. Counterfeit brakes have been discovered with poor-quality steel backing plates and weak or no shim bonding to the backplate, according to the Ford Motor Company. Fakes are often made from compressed wood chips and sawdust.

Replacing expensive smartphone batteries from the manufacturer with no-name or off-brand substitutes can be a costly blunder. Most wireless devices use lithium ion (Li-Ion) batteries because they’re lightweight, capable of holding their charge, and don’t contain toxic metals. Note that even when genuine batteries are produced under manufacturers’ specifications, they’re especially sensitive to physical stress, according to CTIA The Wireless Association, a trade group. Too much pressure on a battery, for example, can cause an internal short-circuit, and overheating. Subject a counterfeit one to the same pressure and it could expand, explode, or catch fire, Samsung says.

Samsung

The fakes shown above stand out because they lack the Samsung logo and a “+” and “-” icon, and the watt-hours value and battery capacity are wrong. Counterfeits might also have protruding or curved contacts instead of recessed flat ones. Learn more at samsung.com/ph/support/skp/faq/1058514.

Six percent of all counterfeit goods seized by U.S. Customs and Border Protection last year were pharmaceuticals and personal-care products. They’re especially dangerous because they could be subpotent, superpotent, expired, or adulterated.

Botox

The genuine wrinkle-smoother is made by U.S.–based Allergan, but in April the Food and Drug Administration (FDA) issued an alert for counterfeit Botox that was distributed by an unlicensed supplier and may have been sold to doctors’ offices and clinics nationwide. The products are considered unsafe because the FDA can’t confirm that they meet U.S. standards.

How to tell the difference: With the fake, the vial is missing the lot number, and the carton doesn’t have any entries next to “LOT: MFG: EXP.” The outer carton and vial show the active ingredient as “botulinum toxin type A” instead of “onabotulinumtoxinA.”

Alli

Lab tests conducted by GlaxoSmithKline, the U.K.-based maker of the real over-the-counter weight-loss product, revealed that a fake, which was sold online, lacked orlistat, the active ingredient. Instead, it contained the controlled substance sibutramine, a drug that shouldn’t be used without physician oversight and that can cause adverse interactions with other medications.

Nonprescription contact lenses

Also referred to as “color” or “fashion” contacts, they’re considered counterfeit if they’re sold without a prescription. “The problem isn’t with the decorative contacts themselves,” says Bernard Lepri, an FDA optometrist. (Contacts are medical devices regulated by the agency.) “It’s the way people use them improperly—without a valid prescription, without the involvement of a qualified eye-care professional.” A poor fit can cause serious eye damage, including corneal scratches, infection, conjunctivitis (pinkeye), and even blindness.

Lenses sold illegally cost as little as $20 from street vendors, at novelty stores, and elsewhere.

Counterfeit goods persist, says David Hirschmann, president of the U.S. Chamber of Commerce’s Global Intellectual Property Center, because consumers are lured by unrealistically low prices. What you can do:

Consider the source. Fakes can be found at flea markets, on eBay, via marketplace merchants, at independent deep-discount and no-name stores, purse parties, swap meets, even mall kiosks. Be especially wary of “copycat” websites that resemble those of well-known merchants and Internet pharmacies.

Question prices that seem bewilderingly below market value. “We all like a deal,” Hirschmann says, “but when it’s too good to be true, it’s probably no bargain in the end.”

Know that your purchase does make a difference. While counterfeiting can’t be stopped, Sandra Bell, deputy assistant commissioner for the Office of International Trade, says it can be slowed. “If shoppers don’t buy fakes,” she says, “then counterfeit goods and the sellers behind them won’t prosper.”

This article also appeared in the July 2015 issue of Consumer Reports magazine.

Copyright © 2005-2015 Consumers Union of U.S., Inc. No reproduction, in whole or in part, without written permission. Consumer Reports has no relationship with any advertisers on this site.