There has been a "concerning" rise in food businesses operating out of people's homes during lockdown, according to the food safety watchdog.
Many of them are selling food through social media, putting further pressure on a hygiene inspection system that is under strain because of the crisis.
And other experts are also worried.
"Little food businesses are popping up like mushrooms in lockdown," said Julie Barratt from the Chartered Institute of Environmental Health (CIEH).
"There are rank outsiders operating off the radar, who think, 'Oh, my mum can cook', and confuse cooking with catering," she added. They sell to locals on apps such as Whatsapp, Instagram and Nextdoor.
Many are failing to register as food businesses, meaning their hygiene arrangements are not checked by local authorities.
But even those that do register are often not getting an inspection - despite new businesses usually being a priority - because the system is struggling to keep up during the pandemic.
Hygiene inspections ceased completely during the first lockdown and since then a scaled-back operation has focused on high-risk cases.
Local authorities are using video calls in a bid to clear the backlog. They allow basic issues to be resolved and reduce the time environmental health officers need to spend on-site. They could be used, for example, to ensure there is a separate sink for washing hands.
But these video calls can never be as effective as in-person, surprise inspections, says Ms Barratt.
They are unable to reveal things such as ingredients past their use-by date, or rat droppings under the cooker.
Indeed, a challenge posed by the new legion of at-home businesses is that even if a physical inspection is required, a 24-hour warning has to be given because it is a private address, so the surprise element is lost.