Food Allergy, Food Sensitivity, and Food Intolerance – What’s the Difference?

Mar 26, 2020 | Gut Health, Immune Health

The terms food allergy, food sensitivity, and food intolerance are confusing and often used interchangeably. It wouldn’t be a big deal if the treatments were the same…but they’re not.

In reality, the conditions are very different – and should be treated differently. While two of the conditions require lifelong management, the third can sometimes be reversed by addressing the root cause. Let’s compare and contrast!

Food Allergy

According to the NIH, a food allergy is “an abnormal response to a food triggered by your body’s immune system.” Specifically, a food allergy is when your immune system overreacts to a particular protein found in that food. The reaction occurs quickly after the food enters the body and includes symptoms such as:

  • Itching or swelling of your skin (e.g., hives)
  • Itching or swelling in your mouth
  • Tightening of the throat and trouble breathing

Allergic reactions occur quickly because they are modulated by Immunoglobulin E (IgE). You can visualize IgE as bomb that goes off whenever it encounters (via eating or breathing) the allergenic food, pollen, dust, pet dander, etc. That bomb results in immediate inflammation – swelling, redness heat and/or pain – of the affected area.

Severe reactions, called anaphylaxis, can be life-threatening. Individuals at risk for anaphylactic shock usually carry an auto-injector device containing epinephrine (e.g., EpiPen®) which slows allergic reaction until additional medical help is available.

Aside from allergy shots (a treatment designed to help the body get used to the allergen), the best treatment is complete avoidance of the allergenic food.

Food Intolerance

Food intolerance, on the other hand, refers to difficulty digesting certain foods. Food intolerances arise because some digestive component is missing – usually an enzyme. For example, folks with lactose intolerance have a difficult time digesting milk and dairy products because their bodies do not produce enough of the enzyme (lactase) that digests milk sugar (lactose). The symptoms of food intolerance include stomach pain, gas, bloating, and diarrhea — all signs that food is not digesting normally.

There are two options for managing a food intolerance – either avoid the food (similar to a food allergy) OR replace the missing ingredient. For example, individuals with lactose intolerance can take supplemental lactase enzymes before consuming dairy products to reduce the gas and bloating that usually results from undigested lactose (i.e. when not absorbed, lactose is fermented by bacteria, the byproduct of which is gas). Since DNA guides the production of enzymes, food intolerances rarely go away.

Food Sensitivity

Food sensitivities, also knowns as delayed hypersensitivities, are more variable than allergies or intolerances. Symptoms may occur within 45 minutes or be delayed up to 72 hours after eating the food — and can impact any organ of the body! For reference, poison ivy is a delayed hypersensitivity. Nothing happens when you rub against the plant, but a day or so later your skin becomes red and itchy.


  • Heartburn / reflux
  • Stomach pain / cramps
  • Constipation / bloating
  • Gas of any kind
  • Nausea / vomiting
  • Diarrhea


  • Fatigue
  • Daytime sleepiness
  • Restless
  • Insomnia


  • Blemishes / acne
  • Eczema or psoriasis
  • Rashes or hives
  • “Rosy” cheeks or flushing

Emotional / mental

  • Depression
  • Mood swings
  • Anxiety
  • Irritability
  • Difficulty concentrating / brain fog


  • Headaches / migraines
  • Aura
  • Hyperactive
  • Tics or twitches

Good news! In contrast to lifelong food allergies and intolerances, most food sensitivities can be reversed. This is because the root cause of most food sensitivities is intestinal hyperpermeability, commonly known as “leaky gut.”

Robust mucosal layer and tight junctions prevent unwanted particles from entering the bloodstream
Degraded mucosal layer and “leaky” junctions allow pathogens and other unwanted particles to enter the bloodstream, resulting in inflammation

Think about it this way – your digestive tract is a semi-permeable tube through your body, allowing your intestinal cells to absorb the nutrients it needs, eliminate components it doesn’t need (via stool), and learn about the outside world in the process.

Fact: Almost 70% of the entire immune system is located in the gut!

Healthy intestinal cells are positioned very close together, forming tight junctions. Tight junctions allow the cells to determine what gets into the body. For example, if you stuffed a pair of nylons with a bunch of chewed-up food, only the juices (i.e., fully digested nutrients) would get through.

However, sometimes the tight junctions open up and allow unwanted particles (e.g. undigested food) to enter the blood stream. For this example, imagine you stuffed chewed-up food into a pair of fishnet stockings. More than just the juices get through, right?

Immune cells (e.g., T cells) positioned just past the barrier are ready to “fight” anything suspicious. The more frequently unwanted particles come through, the stronger the immune reaction to those particles. If the “threat” is bad enough, the immune cells at the barrier may “signal for back-up,” triggering an immune cascade that can impact any organ system. For this reason, symptoms can appear in the gut (pain, gas, bloating), skin (eczema, psoriasis, rosacea), joints (pain), or brain (migraine, difficulty concentrating, insomnia, depression).

When the gut is leaky, the immune system gets turned on, or activated, after every meal, resulting in chronic, low-grade inflammation. This chronic, low-grade inflammation has been implicated in many autoimmune diseases including Hashimoto’s thyroiditis, Celiac disease, fibromyalgia, and irritable bowel syndrome (IBS) as well as depression.

Good news! Once you heal the gut and re-close the junctions, no more undigested food particles can enter the bloodstream. With time, the immune system calms down and stops reacting so strongly to those foods – and sometimes stops reacting at all.

Here’s a chart summarizing everything

ONSETQuickly! Within seconds, up to 1 hour after ingestion30 minutes to two hours after ingestion (basically, once the food reaches the small intestine)From 45 minutes up to 72 hours (that’s 3 days!) after ingestion
ACUTE OR CHRONICUsually acute, rarely chronicLess related to immune system; more related to how well your body is digestingUsually chronic, rarely acute
ORGANS INVOLVEDUsually limited to airways, skin, and the GI tractUsually limited to the GI tractCan affect any organ system in the body
MECHANISMIgE – rapid and aggressive memory responseMissing a digestive component (e.g., enzyme)Various immune cells releasing mediators
THE CULPRITThe Big 8: milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, soybeansVaries; depends on missing componentVaries
HOW MUCH FOOD IS NEEDED?Only 1 molecule of allergic food can trigger reactionOften dose-dependent and can vary from small amount to large amountOften dose-dependent and can vary from small amount to large amount
TREATMENTAvoidanceAvoidance — or replace the missing component (e.g., enzyme)Heal the root cause to reverse food sensitivities

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