The biggest cooking oil bottler for UK shops has said it only has a few weeks' supply of sunflower oil left.
Ukraine and Russia produce most of the world's sunflower oil and the war is disrupting exports, Edible Oils told the BBC.
The company, which packages oil for 75% of the UK retail market, is ramping up supplies of other oils for shoppers.
Meanwhile, manufacturers of foods that contain sunflower oil, like crisps, oven chips and cereal bars, are reworking their recipes.
The Food Standards Agency has advised people with allergies to look out for extra information from shops and food makers.
Kim Matthews, commercial director at Edible Oils said 80% of the global supply of sunflower oil comes out of Russia and Ukraine.
"So obviously, with everything going on out there, we physically can't get sunflower to be coming out of the country," he said.