Making Sense of Adult-Onset Food Allergies

Sounds like a food allergy.

But hold on, don’t food allergies normally arise in childhood? Not always. Strange as it might sound, you can develop a food allergy at any time - to foods you have eaten without consequence all your life.

That’s right: the avocado in that chicken sandwich could have gone from an old favorite to a potential threat in the eyes of your immune system overnight.

So, What Causes a Food Allergy?

When you eat something you are allergic to (in this case the avocado), the body senses that a specific protein in that food may be harmful and triggers an immune response, producing antibodies called Immunoglobulin E (IgE). [1] These antibodies travel to cells that release chemicals like histamine, which cause an allergic reaction. This reaction usually causes symptoms in the nose, lungs, throat, or on the skin[2]. 

And it’s not just a one-time thing: the body will “remember” this reaction and when you eat the food again, the same histamine response is triggered[3]. Sayonara avocado toast.

How Do You Know It’s a Food Allergy?

If you have a food allergy, you’ll probably know about it, as the symptoms tend to be acute and severe. Most people develop symptoms within 15 minutes to one hour of eating the responsible food and may experience any or all of the following:

  • Hives
  • Swelling lips
  • Itchy skin
  • Coughing
  • Wheezing
  • Vomiting
  • Shortness of breath.
  • Anaphylaxis is the severest allergy.

Allergy vs Intolerance

So, you don’t break out in hives or start swelling after eating a specific food, but a few hours later, you’re feeling exhausted, bloated, and below par. You’re likely experiencing a food intolerance or sensitivity rather than an allergy. The symptoms of food intolerances are wide-ranging, but may include:

  • Eczema
  • Acne
  • Fatigue and sleepiness not relieved by rest
  • Bloating
  • Constipation
  • Loose bowels
  • Runny nose and mucus
  • Moodiness
  • Sweating
  • Dry little bumps or pimples on the upper arm.

Unlike food allergies, intolerances don’t involve the immune system. They occur when we are not able to digest, absorb, or process food adequately for some reason, e.g. due to a lack of digestive enzymes or insufficient hydrochloric acid in the stomach[4]. Dairy intolerance, for example, is often due to a lack of the enzyme required to break down lactose. This inability to break down lactose leads to a build-up of liquid in the GI tract, creating diarrhea and bloating.[5]

While food intolerances don’t cause an immediate or life-threatening reaction, they should still be taken seriously. Any reaction indicates that your body is under some level of distress, so it’s important to take notice and remove the responsible food from your diet. Continually eating foods to which you are sensitive can create inflammation and damage the delicate gut lining.

If you experience any of the above symptoms but are not sure what’s causing the intolerance, it’s worth visiting a nutritionist or naturopath to help you pinpoint which food (s) you are sensitive to. 

Where Did All These Allergies Come From?

Look around the average workplace, classroom, or family and you’ll more than likely find at least one person with a food allergy or intolerance. There’s no doubt about it, allergies are on the rise. While we don’t know for sure exactly what’s behind the increase, experts do have a few ideas.

Our lives are too clean

Some researchers believe that our hyper-clean lifestyles might have something to do with the noticeable rise in food allergies. In more primitive times, our immune systems were kept busy battling germs from animals, our environment, and other humans, but now, thanks to better hygiene practices and antibiotics, most of our lives are so clean that the immune system sometimes shifts its focus to harmless substances and even our own body cells, triggering allergies and auto-immune diseases.

Studies into asthma and allergies indicate there may be something to this theory. In the 1990s, Dr. Erika Von Mutius embarked on a study to compare the rates of allergies and asthma in East and West Germany. She expected that children growing up in the poorer, dirtier, and generally less healthful cities of East Germany would suffer more from allergy and asthma than children in West Germany, with its cleaner and more modern environment.

In reality, the opposite was true. Children in the polluted areas of East Germany had fewer allergic reactions and fewer cases of asthma than children in the West. This led Dr. Mutius to posit the “Hygiene Hypothesis” - that the immune system requires some level of dirt and microbes to prime it for the challenges it will encounter in the future. Children exposed to more microbes (and those who had the most exposure to other children) developed greater tolerance for the irritants that cause asthma and allergies.[6]

The U.S. Food and Drug Administration (FDA) agrees with the Hygiene Hypothesis, recommending that infants be exposed to some level of natural dirt and germs early in their life to prime the immune system.[4]

Food allergies and sensitives are complex conditions that we are only just beginning to understand. In another blog, we explain the role the gut plays in food sensitivities, and we’ll provide some simple strategies to help manage your food allergy or sensitivity.


[1] American Academy of Allergy Asthma and Immunology.
[2] Dr  Axe. Food Allergy Symptoms and Six Ways to Reduce them.
[3] American Academy of Allergy Asthma and Immunology.
[4] Middlestead, M. The Shape Diet.Penguin Group, Auckland. 2004.
[5] Dr Axe. Food allergies. Dr  Axe. Food Allergy Symptoms and Six Ways to Reduce them.
[6] Hygiene hypothesis