What is the difference between food allergy, food sensitivity and food intolerance?
Food allergies, food sensitivities and food intolerance are often used interchangeably and inappropriately. In fact, there is active debate in scientific and medical circles as to how to define and use these three terms. The general consensus is that food allergy can be defined as any adverse reaction to food that involves our immune system. This further breaks down into two kinds of reactions, food allergy and food sensitivity. Food intolerance does not involve the immune system.
Food Allergy:
Perhaps the best known example of food allergy is also its least common and most dangerous. Anaphylactic shock is a severe hyper-reaction of the immune system caused by a massive release of histamine and other chemical mediators from certain types of white blood cells called mast cells and basophils. Not everyone with food allergies experiences anaphylaxis though. The immunological triggering mechanism that causes the mast cells (and basophils) to release their chemicals is called IgE and is a very well understood phenomenon. This underlying mechanism is considerably different from the triggering mechanisms found in food sensitivities. The most common foods implicated in food allergy are peanuts, other nuts, shellfish or foods containing sulfites. People with anaphylaxis can die within minutes if they ingest even one molecule of their allergic food.
Food Sensitivity:
Food sensitivity (also known as delayed food allergy) is quite another story. Delayed reactions manifest in many different ways as they can affect any organ system in the body and can take from 45 minutes to several days for symptoms to become apparent. The delayed onset of symptoms and complex physiological mechanisms involved in food sensitivities make them an especially difficult puzzle to try to solve either on your own or with most laboratory serum tests. In fact, food sensitivities often go undiagnosed or misdiagnosed. The treatments prescribed usually provide only temporary relief that mask the symptoms instead of addressing the root cause of the problems.
The differences between the two kinds of immune-mediated adverse food reactions are summarized in the table below.
| Item compared | food Sensitivities | food allergies |
|---|---|---|
| Body Organs Involved | Any organ system in the body can be affected | Usually limited to airways, skin, gastrointestinal tract |
| Symptom Onset Occurs | From 45 minutes up to 3 days after ingestion | From seconds to 1 hour after ingestion |
| Are symptoms acute or chronic? | Usually chronic, sometimes acute | Usually acute, rarely chronic |
| Percentage of Population Affected | Est 20-30% | 1-2% |
| Immunologic Mechanisms | White blood cells Antibodies: IgG (and subclasses) IgM C3, C4 | IgE |
| Non-Immunologic Mechanisms | Toxic , pharmacologic | None |
| How much food is needed to trigger the allergy? | From small amount to large amount; often dosage dependent | 1 molecule of allergic food needed to trigger reaction |
Food Intolerance:
Food intolerance can produce some digestive symptoms that are similar to food sensitivity but it doesn't involve the immune system. Instead, when the food in question is consumed, it is not properly digested and begins to ferment inside the gut. The best example of food intolerance is lactose intolerance. This condition is characterized by bloating, loose stools or diarrhea and gas. Lactose intolerance is caused by an inability of the body to produce enough of the enzyme lactase, which breaks down lactose, the primary sugar found in milk. Avoiding milk products or supplementing the diet with lactase enzyme is the best way for a person with lactose intolerance to overcome the problem.