Is nausea after eating be a food allergy or intolerance?

See a Doctor: There are many causes of nausea and food allergy could be one of the them. If one is experiencing nausea then an evaluation by one's pcp is needed.

Food allergies: Milk, eggs, wheat, soybeans, fish, crustacean shellfish, tree nuts ; peanuts cause 90 % of food allergic reactions. Up to 15 million americans suffer from food allergies ; need to avoid not only certain foods but any ingredient that contains proteins derived from them. In some cases, anaphylaxis can result. See http://www.Boston.Com/lifestyle/health/blog/nutrition/2013/11/the_dangers_of_dining_out.