No commercially available crops contain allergens that have been created by genetically engineering a seed/plant. And the rigorous testing process ensures that will never happen.
There are thousands of proteins in the diet, and only a small fraction of them cause allergies. With respect to GMOs, the U.S. Food and Drug Administration has specifically focused on allergy issues and requires companies to analyze the proteins they are using in the biotech process to determine if the proteins are allergenic. This entire process is well regulated and monitored and takes years to complete. The only documented case where an actual allergen was introduced into a plant by genetic engineering occurred during an experiment trying to improve the nutritional quality of the soybean by using a Brazil nut protein. The Brazil nut protein was in fact identified as an allergen in the new soybean, which prompted the researchers to halt the experiment, and this new soybean never entered the market.