An allergic reaction to food may not appear until the immune system reacts to it. There can be a delay of several hours depending on what you eat and how much you consume. Other cases can develop within a few minutes. It can be made to last longer by scratching at it. Additionally, this can increase your risk of skin infections. In time, your symptoms will subside as your immune system settles down. Minor symptoms can be alleviated with antihistamines and topical creams. You should see the rash subside within a couple of days. Although rare, it is possible to have a second wave of food allergy symptoms after the initial reaction. If you think your food allergy rash has become infected, call your doctor. There may be inflammation, pain, and discharge as symptoms. Infection can also increase the size of the rash.