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Food Allergy, Intolerance, or Sensitivity?

While we were still dating, I sent my husband to the emergency room by unknowingly giving him some cashews. Sorry dear! 

Earlier in my career, my understanding of food allergies had been mostly academic. I knew the importance of managing cross-contact in a commercial kitchen. I knew around 90% of food allergies are caused by the same ten foods and that these allergens must be declared on food labels. Sure, I knew other people with food allergies, but never an immediate family member with whom I was eating day-in and day-out. Needless to say, after meeting my husband and the whole cashew incident, my experience with food allergies now is much more personal! 

Because the number of food allergies, intolerances, and sensitivities is growing, and in light of Food Allergy Awareness week, let’s look at the differences between these three issues.


Food allergies often appear early in life and elicit a dramatic response from your immune system. While it’s quite complex, this involves antibodies and immune cells being activated to release pro-inflammatory chemicals to kill off specific food proteins  the body views as an enemy. Reactions are quite immediate and will appear within minutes and up to two hours after exposure. This may manifest in a combination of both internal swelling, like your throat tightening and airways closing up; as well as external inflammation, like skin redness, hives, puffy eyes, or itching around the face and mouth. Digestive distress like nausea, vomiting, and cramping is also common.

The ten most common food allergens are peanuts, tree nuts, milk, eggs, wheat, soy, fish, shellfish, sesame, and lupin. While egg and milk allergies usually go away as the child grows up, the majority of peanut, tree nuts and seafood allergies persist into adulthood. While 90% of all food allergies are caused by these ten foods, more than 170 foods have been associated with food allergies. 

The best way to diagnose a food allergy is consulting an allergist to do a skin prick test or a blood test (RAST) looking at immune system responses. 

Management of food allergies consists in complete avoidance of single trigger food(s), action plans for accidental ingestion, education of family members and carers, as well as environmental control. 


Food intolerances are usually caused by the inability to fully digest certain foods and involve reactions to specific chemicals common to many different foods and/or additives (ie. preservatives and food colors). Reactions tend to be less severe and less immediate than allergies (ie. hours to days), but often can cause allergy-like symptoms, such as headaches, mouth ulcers, eczema and sinus congestion - as well as the more common digestive issues of stomach and bowel irritation. Many people spend years with an undiagnosed food intolerance because they only got the allergy-like symptoms and did not consider a direct connection to food! 

Intolerances tend to be dose-dependent: you may be able to have a little bit of the food, but over a certain amount can be problematic. To make it even more complicated, that threshold can change over time depending on additional factors such as stress or age. Unlike a food allergy, there are no blood tests or skin pricks available for diagnosis. Instead, we follow a specific elimination diet and subsequent food chemical challenges to determine which chemicals are a problem and how much is tolerated. Although people might have a life-long susceptibility, tolerance levels can vary and symptoms can be eased. 


As if there wasn’t enough grey area between food allergies and food intolerances, enter food sensitivities! The most common food sensitivity is irritable bowel syndrome (IBS). Although there is still much to be learnt in this area, there has been tremendous progress in the last few years identifying the role of our gut bacteria in digesting foods for us. Think that apples, bread, broccoli, cabbage, onions, legumes, honey, and a host of other sugars are actually digested by these helpful tenants rather than ourselves. Hence, when the colonies are disrupted- from things like stress, antibiotics, heavy alcohol consumption, food poisoning or a low nutrient diet- our ability to digest these foods become compromised. Enter bloating, gas, abdominal cramping, constipation and/or diarrhoea! 

As with food intolerances, the onset of food sensitivities can happen at any time and there is no simple blood test to diagnose the problem. Instead, we go through a (different) process of elimination, challenges and reintroduction to determine the problem areas and slowly support the strengthening of the bacterial colonies. With gut bacteria improvement your tolerance to previous trigger foods can increase.

As we mentioned before, there is quite an overlap of symptoms between these three conditions, although the mechanisms behind them, treatment and outcomes are completely different! Many people go for years avoiding certain foods or food groups unnecessarily and/or putting up with highly uncomfortable symptoms that could be easily managed with the right dietary approach.


The first step is to talk to your GP who may refer you to a specialist to check for food allergies, coeliac disease or other gastrointestinal issues. If you’re struggling to adjust your diet to cope with a new diagnosis, we can definitely help! If you continue having IBS or other digestive problems, it may be time to work with one of our nutrition professionals on an elimination or low FODMAP diet. 

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