Traces of nuts have been found in McDonald's buns and English breakfast muffins, prompting the fast food giant to issue a urgent allergy warning.
The chain has admitted that nuts or peanuts may have entered its supply chain and come into contact with the popular menu items.
Warning notices have been put up on everything from restaurants and self-order screens to delivery apps and drive-thrus saying the risk is "until further notice".
It is not known how many McDonald's outlets are affected.
A spokesman for McDonalds told the Mirror Online it is only a “temporary issue”.
The spokesman said: “We have been made aware that traces of nuts and peanut may have entered our supply chain and come into contact with the Buns and English Breakfast Muffins served in some of our restaurants.
“We have already introduced clear signposting in the restaurants affected at the front counter, on self-order screens, at drive-thru and on the click & collect and UBEREATS McDelivery apps.
“Anyone with any concerns should speak to the restaurant team or contact customer services. We have also notified Anaphylaxis Campaign who has alerted its members.
“The health and safety of our customers is our absolute priority, and this is a temporary issue which we are working to rectify as quickly as possible.”
But the nut warning news has sparked complaints on social media.
Charlo Folland wrote: "Very disappointed to learn today that your burgers no longer cater for people with nut allergies due to the buns now carrying the nut warning. Yet another food chain who are failing to support those with allergies."
Fiona Hunter added: "So annoyed and upset for kids with severe allergies who now can’t eat here!.
"Why do u need nuts on buns anyways?! And cross contamination too .. (I’m gutted as I can’t get my favourites either.. severe nut allergy - not worth the risk!).”
From London, a Twitter user calling themselves Moli, tweeted a picture of one of the notices that went up this week.
He wrote: "Another reason not to eat McDonald's. The buns and muffins might contain nuts or peanuts."
In a message posted on their website , Anaphylaxis Campaign said: "We have been alerted by McDonald’s UK that traces of nuts and peanuts may have come into contact with the Buns and English Breakfast Muffins served in some of their restaurants.
"Clear signposting is already in place in the restaurants affected at the front counter, on self-order screens, at drive-thru, on the click & collect and UBEREATS McDelivery apps.
"This is a temporary issue and it will be communicated by alert from us when resolved."
Anyone with concerns should speak to the restaurant’s team or contact McDonald’s customer services 0370 524 4622