But the warnings didn’t stop social media users from discussing and sharing the unproven recipes online.
In the first week of May, there were just a couple hundred posts discussing homemade baby formula on Twitter, according to an analysis by Bloomberg News.
The next week, that number jumped to almost 5,000 tweets – a 2,100 per cent increase.
“If you are affected by this, don’t panic,” said one tweet. “Millions of us grew up on homemade formula… your baby will be fed and happy and probably have fewer tummy upsets.”
On Facebook, posts sharing a photo for a 1960s recipe for homemade baby formula as a workaround to the shortage were by far the most viral on the platform.
Posts containing the recipe photo were shared in hundreds of Facebook groups with names like “Country Girl’s Dream Spaces” and “Mommy Talk Madness”, generating 95,899 interactions in the past year, according to an analysis on CrowdTangle, a social media web tool owned by Facebook parent Meta Platforms Inc.
Though not everyone in the Facebook groups liked or shared the posts, the DIY recipe may have reached as many as 12.5 million people, the analysis showed.
On some of the posts, Facebook applied a label saying the information listed could mislead people.
But on others, including one that collected nearly 1,000 likes and shares, the label wasn’t applied.
The company appeared to be labelling posts inconsistently “based on very basic text patterns, such as ‘formula recipe’,” said Ms Edelson, the misinformation researcher.
The recipe was also shared widely on Meta’s Instagram photo-sharing app, generating hundreds of likes and shares. Similar to Facebook, many of the Instagram posts didn’t carry the misleading label.
On Google’s YouTube, dozens of videos sharing DIY baby formula recipes were hosted on the video site and shared across other platforms, including Twitter and Facebook, collecting hundreds of likes and shares.
The most popular videos had tens of thousands of views and included ads, appearing after a simple search string – “homemade baby formula” – despite YouTube’s promises that it doesn’t allow or promote content containing health misinformation on search and recommendations on the site.
YouTube removed some videos from its site, but only after Bloomberg News reached out.
The same simple search on ByteDance Ltd’s TikTok app brought up just as many results, but the videos were even more viral on the platform.
Half a dozen of the most popular search results containing untested formula concoctions saw at least 1.5 million views on the platform, according to a review by Bloomberg News.
After Bloomberg reached out for comment, TikTok removed results for “homemade baby formula” and added a notification for users that some of the posts that would have appeared are in violation of community guidelines.
Many of the instructions shared online were based on a homemade recipe from the Weston Price Foundation, a non-profit based in Washington, DC, that has also advanced false claims about vaccines, cholesterol and Covid-19.
“A better, healthier homemade baby formula recipe,” tweeted Ms Darla Shine, the wife of former President Donald Trump’s onetime communications director, attaching a link to the group’s recipe. “Please pass around.”
Her tweet collected 150 likes and shares. The link was shared hundreds more times on Twitter, a CrowdTangle analysis showed.
On Facebook, the same link was shared hundreds of times, generating 23,600 likes and shares on the platform. It collected 2,400 more interactions on Instagram. Ms Shine did not respond to a request for comment.
Dr Abrams, the paediatrician, said he was “very familiar” with the group’s formulations and considered them “risky”.
