Some 57 people, mostly young children, have become infected with salmonella in an outbreak linked to Kinder Surprise eggs.
Chocolate firm Ferrero is recalling some batches of the eggs as a precaution while investigations continue into the link, the Food Standards Agency (FSA) said.
No deaths have been reported but around 77% of the cases involve children aged five and under.
In an alert, the agency said the recall is due to a “potential link to a salmonella outbreak”.
The products affected are the 20g eggs or the three-pack of eggs, all with a best-before date between July 11 2022 and October 7 2022.
Ferrero has recalled the products and people are being advised not to eat them.
Anyone who has bought products with those use-by dates can contact the Ferrero consumer careline on firstname.lastname@example.org or 0330 053 8943 to obtain a full refund.
The FSA said the eggs have all been manufactured at the same factory, and other Ferrero products are not thought to be affected.
Investigations so far have been led by the UK Health Security Agency (UKHSA), Public Health Scotland, Public Health Wales and Public Health Agency Northern Ireland.
Symptoms of salmonella include diarrhoea, stomach cramps, nausea, vomiting and fever.
While most cases resolve in a few days, symptoms can be severe and lead to hospital admission, especially in the very young and those with weakened immune systems.
Tina Potter, FSA head of incidents, said: “We welcome the precautionary approach being taken by Ferrero and are advising consumers not to eat any of the products listed in the FSA alert.
“It is really important that consumers follow this advice to avoid the risk of becoming ill with salmonella poisoning.
“We know that these particular products are popular with young children, especially as Easter approaches, so we would urge parents and guardians of children to check if any products already in their home are affected by this recall.
“The food business involved has voluntarily carried out this product withdrawal and recall and we are working closely with them and their competent authorities to identify the precise cause of this outbreak.”
Dr Lesley Larkin, a surveillance lead at the UKHSA, said: “Anybody with concerns that they have symptoms of salmonellosis should contact their GP or call NHS 111.
“Salmonella can be spread from person to person, so anyone affected should adhere to good hygiene practice such as washing hands thoroughly after using the bathroom and avoiding handling food for others where possible, if you have symptoms.”