Rashes, stomach pain, bloating … when you have a reaction to food that makes you feel unwell, it can be tough to know whether it's an allergy or just intolerance.Although the symptoms may be similar, food allergy and food intolerance are quite different.Food intoleranceWhen you have an intolerance to certain foods, it often means that you are missing the enzymes needed to digest them properly. The symptoms caused by these reactions are usually in the gut, such as bloating, diarrhoea, constipation and IBS. You may also experience skin problems, such as eczema.It may be that you may need to have a large serving of a certain food to trigger intolerance, while it is possible to experience an allergic reaction after only a trace amount.More about food intoleranceFood allergyIf you have an allergy, your immune system overreacts to an otherwise harmless allergen by producing antibodies called Immunoglobulin E (IgE). This can cause severe reactions, including the life-threatening conditions known as anaphylaxis.More about food allergyYour symptoms – and what you should do about themIf you have symptoms that are causing ongoing discomfort, it's important to visit your GP to find out more. If you or your child are experiencing symptoms such as wheezing, dizziness, or swelling of the mouth, lips, throat, or tongue shortly after eating a certain food, you should go to A&E, as this could indicate a dangerous allergic reaction.Nearly all foods can cause allergies, but some of the most common culprits are nuts, cow's milk, and shellfish. If you have a food allergy, you will need to avoid that food completely. Read our tips on how to avoid gluten, dairy and other food allergens.If you have food intolerance, you will need to manage your diet carefully. There are a number of symptom relievers that can help.