The difference between allergy and intolerance

Food intolerance is usually related to the inability to process or digest certain foods. If you have a food intolerance, you may be able to eat small quantities of the food in question without experiencing any problems. When there is a reaction, it is usually unpleasant, with symptoms such as diarrhea or nausea, but does not cause immediate and severe health problems. The reaction may occur after the food is consumed or build up gradually over time. 

The most common example of a food intolerance is lactose intolerance, which affects up to three-quarters of the adult population. Lactose intolerance occurs when a person cannot digest lactose – the sugar found in milk – because their gut is not producing enough of the enzyme lactase. The symptoms can include flatulence, diarrhoea or constipation, stomach cramping, or nausea. Some people with lactose intolerance can have small amounts of food containing lactose, while others find they are better off avoiding it altogether. It is also possible to take lactase enzyme pills to aid digestion of lactose.   

…how the body responds to foreign substances. Intolerance is not caused by the immune system but by poor digestion of certain substances. Allergies, on the other hand, cause the immune system to produce IgE.

Symptoms caused by an allergic reaction or as a result of food intolerance include: 

• Nausea 
• Stomach pain 
• Diarrhoea 
• Vomiting 

Symptoms associated with a food intolerance but not with an allergic reaction include: 

• Gas, abdominal cramping, or bloating 
• Heartburn 
• Headaches 
• Irritability or nervousness 

Symptoms associated with a food allergy but not with intolerance include: 

• Rashes, hives, and itchy skin 
• Shortness of breath and wheezing 
• Chest pain 
• Sudden drop in blood pressure, feeling faint 
• Difficulty swallowing or breathing 
• Swelling, often around the face or throat 
• Anaphylaxis, a medical emergency that can lead to loss of consciousness 

If you think you may have a food allergy, chances are you have already experienced a severe reaction. You should visit a doctor and have allergy tests. If you are diagnosed with a food allergy, you must avoid consuming that food. 

If you think you may have a food intolerance, keep a diary of the foods you eat and symptoms when they occur. The usual treatment for an intolerance is to eliminate the food from your diet and track symptoms. You should always consult with a doctor before making any dietary changes to avoid nutritional deficiencies that can cause other health problems. 

Whether allergic or intolerant, you will have to learn to read food labelling and ingredients carefully.

If you have a reaction after eating a particular food, you should see your doctor to determine whether you have a food intolerance or a food allergy.

If you have a food allergy, you may be at risk of a life-threatening reaction called anaphylaxis, even if past reactions have not been severe. You should learn how to recognize a severe allergic reaction and know what to do if one occurs. You may need to carry an emergency epinephrine shot in case of an emergency.