The consumer genetics market is booming. In 2017, the number of people who took direct-to-consumer ancestry tests more than doubled, reaching over 12 million customers.

The at-home DNA testing craze is quickly expanding outside of ancestry, too. A wave of new tests claim to make all sorts of personalized lifestyle recommendations—from skincare products to diet—based on your genes. But experts say that while genetics certainly underpins many of our characteristics, there’s little scientific evidence that the genetic element of these tests makes the interventions they recommend especially effective.

Many of these tests contain a survey or questionnaire about your habits, health and other personal information. While the tests often do provide some insights about your DNA, their product recommendations might come mostly from analyzing your answers to the survey and common-sense advice. “When someone who is selling you a test says you need this product, you should question their motives,” says James Evans, a physician and geneticist at the University of North Carolina School of Medicine.

Here are some tests you might want to think twice about before sending away a DNA sample.

Nutria

The pitch: Lean Cuisine, the well-known purveyor of frozen meals, is trying out a new meal-planning service that involves a DNA test. It claims that its “genetic markers help determine your customized nutrient intake,” but the service also includes a survey that asks about your food preferences, allergies, and lifestyle.

The price: At $79 for eight weeks (it’s in a trial phase), the program offers recommendations for recipes, dining-out options, and prepared meals (probably from Lean Cuisine).

The science: It also includes an app that allows you to connect with a nutritionist. That’s probably more useful than the DNA analysis: a recent study published in the Journal of the American Medical Association found that diets based on DNA results didn’t help people lose weight. Other companies, like Nutrigene and LifeDNA, want to sell you vitamin supplements on the basis of a DNA test.

SkinGenie

The pitch: SkinGenie says it will give you personalized recommendations of skincare products based on a lifestyle quiz and a DNA analysis. The company says this can be done without the DNA analysis, but it can give you a “more accurate assessment” with a DNA sample.

The price: The skincare assessment costs $59, and that's after purchasing a DNA test kit through LifeNome or uploading your raw data from 23andMe, Ancestry.com, or another company. If you just want to view the product ranking without the skin assessment, you can upload your DNA data at no cost.

The science: SkinGenie’s report looks at 120 genetic markers associated with more than 30 different skin characteristics. It uses this genetic readout to give you a personal ranking (out of 10) of skincare products based on their active ingredients. SkinGenie says these recommendations are based on thousands of research studies. But Evans says our “limited knowledge about how genes are involved in the integrity of our skin can’t be used to design tailored products or care”—at least not yet. Plus, factors other than genetics, like diet, weather and pollution, also have a big impact on our skin.

Vinome

The pitch: Promoted by Helix, a sort of app store for DNA products, this company says it will curate wines for you on the basis of your DNA.

The price: You have to get an $80 DNA test done through Helix, and then purchase the Vinome profile for $29.99. Vinome says it uses “10 genetic markers related to smell and taste” to identify eight unique profiles, but it also asks you to take a taste preference survey. The company then wants to sell you wine—individual bottles or a membership program—after you get your results.

The science: Researchers have found that certain people are predisposed to hate the taste of brussels sprouts or cilantro, but your inclination for certain wines is probably a lot more complex.

Spareroom

The pitch: The company makes a mobile app that helps you find a roommate. But it’s piloting a new service that uses a DNA sample and an online personality test to match you to a compatible one.

The price: After you submit a spit sample, SpareRoom gives you a report that shows how your genetics influence 14 characteristics, like spontaneity, optimism, stress tolerance, self-awareness, and confidence. The company hasn’t yet set the price it will charge when it rolls out the service in the US and UK.

The science: While studies have found genetic links to mental and personality disorders, experts disagree on how much of our character and temperament is actually influenced by our DNA.

The problem with these tests and their ilk, experts say, is that we just don’t know enough about the complex interactions of our genes yet to make these kinds of personalized recommendations.

So, why market these services as DNA tests when DNA information can’t yet be harnessed to make personalized recommendations?

“When a new area of science emerges that’s hot and sexy, it becomes a marketing tool,” says Debra Mathews of the Johns Hopkins Berman Institute of Bioethics. As she points out, a similar fad popped up during the heyday of stem cell research: beauty companies started marketing all sorts of “regenerative” skincare products that claimed to contain stem cells.

Beyond the quick buck, though, many of the companies are also playing a long game. Once they have sell customers’ data, they can compile it and sell it to researchers (for the record, SkinGenie says it doesn’t). That’s where there’s real money to be made.

“I certainly don’t think you want to relinquish the rights to your genetic information to get this advice,” Mathews says. Her advice before swabbing or spitting: “Read the fine print.”

Update: This story was modified to make the reasoning clearer and more explicit, and to add comments from SkinGenie. It was also corrected to reflect the fact that it is SkinGenie’s skincare assessment that costs $59, not LifeNome’s DNA testing kit.