In a holiday commercial, Dr. Seuss’s the Grinch receives a 23andMe DNA kit as a gift and logs on to the company’s website to check out his results. He learns he’s genetically likely to move around more than average during sleep and that liking salty snacks is in his DNA. The commercial ends with a voice-over: “This holiday season, give the gift of a DNA kit from 23andMe.com.”

The commercial seems to be aimed at parents and their children. It’s not the first time 23andMe has used popular cartoon characters to market its tests. Last year, it launched an ad campaign around the movie “Despicable Me” and its yellow minions.

These commercials are cute and make DNA testing look fun. And they’re clearly working. Clever marketing combined with holiday deals means parents are buying their kids DNA tests from companies 23andMe, AncestryDNA and MyHeritage. But these tests might not be appropriate for all kids, and experts say there are many reasons parents should think carefully before sending their child’s spit through the mail.

Katie Stoll, a genetic counselor and executive director of the nonprofit Genetic Support Foundation in Olympia, Wash., says her concerns around using these tests on minors boil down to the autonomy of the child. “Children should have the opportunity to grow up and decide for themselves whether or not this is information they want to know,” she says of DNA test results.

But parents already make a lot of health-care decisions for their children. How is DNA testing different? For one, direct-to-consumer DNA testing companies don’t fall under the purview of health privacy laws in the United States. The Health Insurance Portability and Accountability Act of 1996, known as HIPAA, protects individuals’ medical information handled by doctors, hospitals and health insurance companies, but it doesn’t apply to the vast majority of DNA kits that people can order themselves.

Many companies also sell customers’ genetic data to third parties, like pharmaceutical companies, and it can be difficult to delete that data once you’ve already consented to it being used for research. Young children can’t give informed consent, and even teens may have a hard time understanding what that means for the privacy of their information.

Beyond privacy issues, health information about a child that’s revealed by a DNA test could have a negative impact on parents’ relationships with their children.

23andMe’s Health and Ancestry service includes reports on a handful of genetic health risks, including Alzheimer’s, Parkinson’s and certain variants of the BRCA genes, which are associated with a higher risk of breast and ovarian cancer. In a medical setting, children are not routinely tested for these health risks because they don’t appear until adulthood.

“These are conditions that are not going to affect children during their childhood, and there’s nothing we would recommend doing differently in childhood to change those outcomes,” Stoll says. “How does knowing that information about your toddler help them?” Instead, it could give parents unnecessary anxiety about a condition that their child may not ever develop.

Hank Greely, a bioethicist and director of the Stanford Center for Law and the Biosciences, says he also worries about children misunderstanding health reports. Greely remembers getting a skin test for tuberculosis as a child. The nurse told him his test results were negative. “I was a kid and I thought ‘negative’ meant bad. I thought I was dying of this thing called TB,” he says.

For many parents, genealogy is the motivating factor in buying tests for their kids. Still, children can learn potentially distressing information from ancestry tests, like finding a relative they didn’t know they had or discovering a family member isn’t actually related to them biologically.

Amy McGuire, a lawyer and director for the Center for Medical Ethics and Health Policy at Baylor College of Medicine in Texas, says many people assume that ancestry tests are harmless, but that’s not always the case.

“People find out a lot of surprising information about their families that I think might be more disturbing to kids than finding out about a disease risk that might happen much later in life,” she says.

For instance, paternity revealed by a genetic test can radically change the dynamics of a family and have lasting impacts on children. In a recent case, a man discovered he wasn’t the biological father of his 15-year-old daughter after buying her an AncestryDNA test. A few weeks after getting the results, he filed for divorce from his wife.

Greely says if kids are really interested in learning about their genealogy, parents should take the tests instead. “You get a better resolution of the ancestry the higher up the family tree you go. You get more details from the parents than you will from the kids and more details still from the grandparents,” he says.

Technically, 23andMe and AncestryDNA, the two biggest providers of consumer DNA kits, say their services are for adults. Customers have to be 18 years or older to order a test, but a parent or legal guardian of a child under 18 may purchase one and open up an account for a child.

Other companies, like Orig3n, New Life Genetics and Mia DNA, offer “lifestyle” DNA kits that are specifically meant for kids. Orig3n’s Child Development DNA test claims to test whether your child has a predisposition for certain sports, is a picky eater or can easily learn new languages. Stoll says results from tests like these could affect how parents would have otherwise raised their children. For example, parents might spend more money on language lessons or sports that their kids might not necessarily enjoy.

One mother we spoke to, who didn’t want her name used to protect her son, says she’ll be taking advantage of holiday sales to buy a few DNA tests for her 4-year-old son, whom she and her husband adopted from Uganda. She says they don’t have any information about his biological family.

She says she’s hoping to use DNA testing to eventually track down a sibling who’s also been adopted or another family member who’s emigrated to the United States. “We understand this might take decades,” she says. “I owe it to him to try to find out as much information as I can about him.”

She also wants to use 23andMe’s health service to test her son. She says she’ll eventually tell her son about what she learns from the tests, once he’s old enough to understand. But she says that won’t be anytime soon.

McGuire says a child’s age, maturity and personality are major factors when deciding to buy these tests for kids or share results with them.

McGuire, who’s a mother of three, says she hasn’t bought DNA tests for her children. But if they asked, she’d take a different approach with each of them. “I have one child who’s a total hypochondriac,” she says. “I don’t think it would be a good idea for him to get genetic testing done for recreational purposes.”

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