When the body's immune system reacts negatively to a particular food it is known as a food allergy. Food allergies can cause a wide range of symptoms, including skin reactions (such as a red itchy rash or swelling of the lips, face and around the eyes), digestive problems (such as stomach ache, vomiting or diarrhoea) and hay fever-like symptoms (such as sneezing and itchy eyes). Symptoms can appear suddenly, within minutes of eating the food, or can take hours or days to develop. Occasionally, severe symptoms can occur, such as swelling of the throat, hoarse breathing sounds, and sudden shortness of breath or wheezing. Food allergies are more common in children than adults because children often outgrow their allergy. The most common foods that children are allergic to are cows' milk, hens' eggs, peanuts, and tree nuts such as hazelnut and cashew.
If the body reacts negatively to a particular food but this reaction is not caused by the immune system, the condition is known as a 'food intolerance' (which is not covered in the NICE guideline).