| Food allergy | Food intolerance | |
| Description | If you have a food allergy, it means your immune system reacts to a harmless food as if it’s toxic. Your body triggers an allergic reaction. | A food intolerance is a bad reaction to something you’ve eaten that does not involve your immune system. |
| Symptoms | Symptoms of a food allergy usually develop a few seconds or minutes after eating the food. These may include: tingling or itching in your mouth itchy red rash swelling of the face, mouth, throat or other areas of your body difficulty swallowing wheezing or shortness of breath feeling sick or vomiting abdominal (tummy) pain or diarrhoea (runny poos) hay fever-like symptoms, such as sneezing or itchy eyes. Some people may develop a severe allergic reaction (anaphylaxis), which can lead to death. | Symptoms can sometimes be vague but may include: bloating and wind nausea (feeling sick) diarrhoea (runny poos) indigestion abdominal (tummy) pain an increase in eczema or asthma. The symptoms can begin straight away or up to 20 hours after you have eaten the food. |
| Age affected | Most food allergies start in childhood. They are most common in young children aged less than 5 years. Even young babies can develop symptoms of food allergy. | It’s unusual to develop a food allergy as an adult. Food intolerance is much more common in adults. |
| Cause | An allergic reaction is often caused by certain types of food. Just 8 foods cause 90% of allergies. Those foods are milk, egg, peanuts, tree nuts, fish, shellfish, wheat and soy. However, any food can cause an allergic reaction. | Any food can cause an intolerance. Lactose intolerance and non-coeliac gluten sensitivity are common food intolerances. |
| Risk of dying | In some cases, a food allergy can be life-threatening. You can go into anaphylactic shock, which means you might have difficulty breathing and/or a sudden drop in blood pressure. If this happens, call 111 for an ambulance. | Symptoms of food intolerance are not life-threatening. |
Your GP will ask questions about your symptoms, including when and how often they occur. If the symptoms are consistent with being a food allergic reaction and appear within a few minutes the first time of eating a particular food, then diagnosis of a food allergy is likely to be straightforward. However, your GP may refer you for a skin prick or blood tests to confirm the allergen concerned. If a food allergy is suspected or confirmed, you should be referred to a specialist for further tests and ongoing monitoring. This may include an oral food challenge. If a particular food allergy is suspected or confirmed, you should not eat the food until cleared by your specialist to re-introduce it to your diet.
Food intolerance is more difficult to diagnose as there are no tests. You may be asked to keep a food and symptoms diary to check for patterns. You may also be referred to a dietitian. The dietitian may suggest a short-term elimination diet.
Allergies tend to run in families, so a baby with parents who have allergies is at has a higher chance of developing food allergy. Some babies develop food allergy even though there is no family history of allergy. Common foods that can cause allergic reactions are peanuts, eggs, fish and shellfish, cow’s milk (dairy), wheat, soy, seeds and tree nuts.