Buying 'dupes' of expensive items is all the rage. These are the products you should be careful when buying cheap.

Jason Wingate, the CEO of Canadian sales and marketing firm Emerald Ocean, told BI any products that need to be applied to the skin were "categories where buying dupes is just asking for trouble."

He said doing so required careful consideration.

"While the packaging might look similar, what's inside could be untested," Wingate said.

Destiny Chatman, from UK savings app TopCashBack, said people should compare ingredients on off-brand products, and avoid anything with clear disparities from the original product.

"No two products will have identical ingredients; however, if major ingredients are different then you should probably pass," Chatman said.

Ant Robinson, from price-comparison website HalfPricePerfumes, warned anyone looking for dupe fragrances to be aware some can be dangerous.

"The idea of a great fragrance at a fraction of the cost might tempt you, but counterfeit fragrances often contain dangerous — and sometimes, downright disgusting — ingredients," he told BI.

The US Customs and Border Protection has warned that counterfeit makeup and perfume products often contain hazardous ingredients and urged shoppers to focus on reputable retailers and sellers.

"Always make sure that the fragrance you're purchasing is from a legitimate retailer so you know that it isn't fake," Robinson said.

Consumers should also exercise caution when purchasing dupes of luxury-brand bags and purses, Chatman said.

"If it visually looks similar to the original to you, then you should buy it but if there are main differences you can point out, then it's likely to also be visible to others," she said.

She said that sometimes, you can only compare a knock-off to its more expensive product when you try both of them, as, purses or bags cannot be tested in-store like makeup or perfume.

For Wingate, electronics and tech "are the biggest no-go" when considering buying a dupe.

"The safety risks from poor components and bad engineering are serious," he said, adding that he has seen counterfeit chargers catch fire and fake batteries leak. "It's not worth risking your safety to save a few bucks."

Stevie Johnson, managing director of influencer marketing agency Disrupt, told BI that large companies that sell tech products have to meet certain safety standards to avoid potential hazards in their products — and you can't be certain that their dupes are complying with those criteria.

He told BI he'd bought a cheap imitation pair of Airpods, which, except for a slightly poor microphone, he felt worked well, and was worth the saving.

But he said people should be wary of dupes of more expensive tech products, especially those that touch the body.