Day 15: Understand food allergies, intolerances, and sensitivities

Food allergy vs food intolerance chart

There are three types of difficulties with foods: allergies, intolerance, and sensitivity. It’s not unusual to see some of these terms used interchangably, and most people aren’t aware of the differences between them, but the differences are important.

Food allergies are when your body perceives a food as a dangerous intruder and mobilizes the immune system (IgE, specifically) to fight it. Reactions may vary from a skin rash to one’s airways suddenly swelling closed, which can quickly become life-threatening.

Food intolerance means that your body has difficulty digesting certain foods. Symptoms are usually digestive problems such as bloating or diarrhea, but may also include respiratory symptoms or headaches.

This chart further explains the differences between these two:

Food allergy vs food intolerance chart

Other common food allergies not listed by the chart include wheat and soybeans. Less common allergens include corn, gelatin, various meats, seeds (sesame, sunflower, and poppy being the most common) and certain spices.


Food sensitivity is controversial in some quarters because it doesn’t always show up in common lab tests. It’s similar to allergies in that it involves the immune system (but the reaction is usually less violent or life-threatening), but similar to intolerance in that reactions to food are usually delayed and may be in proportion to the amount ingested. While not immediately life-threatening, it may do damage to the body. For example, in a person with celiac disease, the reaction to gluten may cause damage to the small intestine. (Learn more about celiac here.)

If you remove all offending foods from your diet for a time, your system may heal to the point where you can again enjoy them in moderate quantities.

Symptoms may include:

  • Bloating or irregular digestion
  • Skin rashes of any kind, including adult acne
  • Runny or stuffy nose
  • Muscle and joint pain
  • Depression and mood swings
  • Foggy head; difficulty with mental focus
  • Autoimmune diseases (such as Graves’ Disease, Hashimoto’s, lupus, MS, rheumatoid arthritis, and more)

Foods don’t cause the autoimmune disease — which often have a genetic link — but food intolerances can add fuel to the symptoms. A common saying is, “Genetics loads the gun, but lifestyle/environment pulls the trigger.”

Which foods are the main cause of food sensitivity is the topic of much debate! Three different websites yielded three different lists:

  • Wheat/gluten, corn, soy, dairy/milk, eggs
  • Cow’s milk, eggs, beans, nuts, cereals/grains
  • Nightshades, eggs, nuts, seeds, gluten, grains, legumes, dairy

Food sensitivities vary from person to person.

So to sum up, food allergies and intolerances are well-known and agreed upon in the medical community, and so finding reliable information about them is not difficult. Food sensitivities, however, are more controversial, and harder to diagnose. This doesn’t mean that they’re not real: just that science is still working out the kinks in the theory.

If you think you may have one or more food sensitivities, here are some books to explore:

It Starts With Food – This book contains some “science-y stuff” (the authors’ term), but leans heavily toward easy-to-read. It explains the “what” and a little of the “why” behind the Paleo diet*, which is an elimination diet that has helped many people with food-related health issues.

Also, see my review of Digestive Health with Real Food. This is the most thorough treatment of food sensitivity that I’ve read, emphasizing that there is no one-size-fits-all diet.

*I don’t think the Paleo diet is something everyone needs to adhere to strictly, and I question its assumptions (that this is the way our ancestors ate), but the proof is in people: Paleo does seem to work for a lot of people with the types of ailments that have exploded in America in the last few decades. It eliminates some of the items that show up on every expert’s food sensitivity list — grains, soy, beans/legumes, and dairy. It does allow eggs, though.

In my next post, I’ll talk about where I’ve landed on this topic, and what I would recommend for someone wanting to take their diet to the next level, once they’ve eliminated sugar and reduced refined carbs.


American Academy of Allergy, Asthma and Immunology  – Definition of allergies/intolerance

American College of Allergy Asthma and Immunology – Detailed info on food allergies

Today’s Dietician – Definition of allergies/intolerance

Mayo Clinic – Difference between a food intolerance and food allergy

Chris Kresser – Gluten sensitivity

Allergy UK – Common food intolerances

Medical News Today – Common causes of food intolerances

Medline Plus – Definition of celiac disease

Very Well article: An overview of celiac disease


I’m not a doctor, nutritionist, or any other health professional. You should always check stuff out for yourself!


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