A Californian start-up will be allowed to advertise a mail order DNA test that screens for a rare genetic condition, after a U-turn by the US regulator.

The Food and Drug Administration (FDA), said the 23andMe product would "provide people with information about possible mutations in their genes that could be passed on to their children".

It had previously banned similar tests.

The 23andMe kit screens for Bloom syndrome, an inherited disease that is most common among Ashkenazi Jews.

It can detect whether a healthy person is a carrier of the genetic variant that causes the disorder, and therefore at risk of passing it on to their offspring.

'No test is perfect'

In a statement, the FDA also said it would provide the "least burdensome regulatory path" for future projects from 23andMe and similar companies.

"In many circumstances it is not necessary for consumers to go through a licensed practitioner to have direct access to their personal genetic information," the regulator added.

The decision contrasts with the FDA's stance in 2013, when it ordered 23andMe to "immediately discontinue" selling its saliva collection tests after failing to provide information to back its marketing claims.

The $99 test had offered users a readout of their genetic code, including a detailed analysis of their health risks.

However, despite giving the Bloom syndrome kit a green light, the FDA cautioned that "no test is perfect" and suggested that the kit should only be used by those likely to carry a relevant gene.

Informative labelling and information on how to follow up with a medical professional must be provided by 23andMe, the FDA said.

'Major milestone'

While welcoming the FDA's decision, 23andMe said it would "not return health results on individually cleared reports" until it had a "comprehensive product offering" in place.

The health tech company, which is backed by Google, has been operating since 2006 and was co-founded by Anne Wojcicki, its chief executive, who married Google co-founder Sergey Brin in 2007.

"This is a major milestone for our company and for consumers who want direct access to genetic testing," she said in a blog post.

"We have more work to do, but we remain committed to pursuing a regulatory path for additional tests and bringing the health reports back to the US market."