The Food Standards Agency (FSA) is advising people with a peanut allergy to avoid consuming foods that may contain mustard, because they could be contaminated with peanuts.
The mustard ingredients - including mustard power or flour - can be found in dips, sauces, salads and pre-packed sandwiches, the FSA said.
It is trying to identify which products may be affected.
Parents of children with a peanut allergy should check the labels of food they are buying and ask restaurants and take-away outlets about foods that might contain mustard, the agency says.
Some of the products being recalled because they may contain peanuts include Dominos dips, SPAR sandwich fillers and salads, and Harvester BBQ sauce.
The Food Standards Agency has traced the contaminated mustard ingredients to a producer in India called GT Agro Industries. One company has been identified as supplying mustard ingredients for use in UK food.
Because of how serious allergic reactions to peanuts can be, the FSA says it is taking a precautionary approach, so that people with allergies can keep themselves safe.
According to the agency, if mustard is present in a food, it should be labelled in bold on the packet because it is an allergen itself.
If there is a risk that mustard could be unintentionally present in food, there will be a "may contain" label for mustard.
Rebecca Sudworth, director of food policy at the FSA, said: “Those with a peanut allergy should avoid consuming products containing mustard as an ingredient until we identify the individual products affected.
"As soon as we have more information, we will update consumers," she added.