Are you Allergic, Intolerant or Hypersensitive? What's the Difference?

Food Allergies are a type of hypersensitivity

Food allergies are potentially life-threatening reactions to foods such as peanuts, tree nuts, shellfish, milk, or eggs. Symptoms come on very, quickly, within minutes of eating the food.

Around two percent of the adult population suffer from food allergies, and it is a lifelong condition.

Food intolerances tend to be delayed reactions. They are not life-threatening, but they can make life very difficult for sufferers. They develop from infancy and originate from our innate immune systems, which means they were likely inherited from your parents. Other hypersensitive reactions occur when the normally protective immune system responds abnormally, potentially causing symptoms and reactions in and out of our bodies.

People often get allergy, hypersensitivity and intolerance confused. You might hear lots of people saying they are allergic to this or that food, when in fact they are not. They have developed intolerance— or a sensitivity reactions to that food.

Let’s try and clear things up:

There are four types of hypersensitivity reactions:

Type I

This is your classic allergy. You have an immediate allergic response, also viewed as a severe type of hypersensitivity reaction. It involves a reaction to small proteins or antigens (molecules capable of stimulating an immune response) carried around on things like pollen. People often say they are allergic to pollen the reality is they are more likely to be allergic to the protein in the pollen which could be many things. Allergens may be seemingly harmless substances such as animal dander, molds (as in hay fever), or pollen. Allergens may also be substances considered innately more hazardous, such as insect venom. Contact with the antigen causes a string of physiological activity which commences with the the release of immunoglobulin E (IgE) antibodies that travel to other cells that release the chemicals that cause an allergic reaction. Things like histamine which makes your nose swell up and feel closed for example. Hypersensitivity reactions include anaphylaxis and allergic rhinitis (stuffy nose).

Type II

This type is antibody-mediated, meaning the antibody binds to a cell-bound antigen (toxin or foreign substance that induces an immune response). Our bodies make antibody to foreign antigens. Drugs are foreign, so we make antibodies to the drugs we take. When the antibody molecule reacts with the antigen, the two surfaces fit together like the pieces of a jigsaw puzzle. There are five types of antibodies called immunoglobulins and they are produced by the plasma cells. The principal antibody of this type II secondary immune response is IgG (immunoglobulin G), and most commonly found in the bloodstream. The most common type II reaction is anemia— or low red blood cell count— Grave’s disease and drug allergies. Type II hypersensitivities are also called cytotoxic hypersensitivities. In some cases, the antigen may be a self-antigen, in which case the reaction would also be described as an autoimmune disease. That’s a topic for a different post!

Type III

This type is mostly characterized by antibody excess, and can occur as a reaction to mold and reactions to certain pharmaceuticals. The antibody in play here is also immunoglobulin G (IgG) but to a soluble antigen. The antigen gets into your bloodstream at an alarming rate, which causes antibodies to be in excess and collect in the blood eventually forming a plaque or clog. Your body sends macrophages (a large white blood cell that “eats” foreign invaders) to clear the plaque which can damage the blood vessel walls and tissues. This reaction can cause arthritis, serum sickness, hepatitis and inflammation.

Type IV

This type is one of the most common reactions that people experience. It is generally a cellular response, not an antibody response. It is more innocuous than other types because it is generally a delayed response. The reactions with this type most commonly seen are food sensitivities or intolerances (including gluten sensitivity) and contact hypersensitivities that cause things like allergic dermatitis (rash, blisters, welts, hives) which you can get from contact with poison ivy, poison oak and poison sumac and even chemical-based substances and metals like latex and chromium. Tissue-transplant rejection is also characterized by type IV reactions. Symptoms in the gut from food sensitivities will show up in Type IV reactions more generally as diarrhea. Type IV hypersensitivities are not mediated by antibodies like the other three types of hypersensitivities. Rather, type IV hypersensitivities are regulated by your super awesome defender T-cells. :)

Are you experiencing a food intolerance or food allergy? Intuitively pay attention to potential food triggers and then experiment with your own elimination, or consult a nutritionist (for food concerns) an allergist or a gastroenterologist for lab testing and root cause analysis and protocols for healing.

I hope this helps to explain the various types of reactions that can result from the four different types of hypersensitivities. The term hypersensitivity is not just a catch-all word for unexplainable malaise, but a scientifically definable immune response that leads to harmful and uncomfortable reactions in our bodies, disease and even autoimmune conditions.

For more detailed information and discussion of tests for hypersensitivities, have a look at this hypersensitivity summary under the Microbiology section at Lumen Learning.