Can you imagine how difficult it must be to have a food allergy? In this post, we break down what an allergy is, what it causes, and how it’s treated.
Imagine this: You’re 11 years old, and you go to the beach. Your family doesn’t typically go to the beach so this is a new exciting experience for you. To celebrate, your family indulges at a crab shack, where there’s more crabs that you could ever eat. They are perfectly cooked, buttery, well seasoned. You are loving it, having the time of your life. Suddenly, you feel a slight tingling in your throat, your heart begins racing. You feel this surge rushing through your body. You start breathing faster, and you feel like you can’t catch your breath. Your tongue begins to swell, making breathing even worse. Your parents quickly realize what is happening and call 911. You end up in the hospital for several hours, but manage to come out alive.
You had an allergic reaction, also called anaphylaxis. You were likely treated with a variety of medications including Benadryl and Epinephrine.
The Immune System
The body has a protection mechanism called the immune system. The immune system is a complex, multifaceted organization of proteins, cells, and tissues. Without it, our bodies would be vulnerable to attack from outside invaders, known commonly as foreign bodies or antigens. To understand allergic reactions, we have to start here. First, let’s talk about the origin tissues of the immune system.
Immune Cell Types
There are many types of cells in the body, and they can be categorized in several different ways. One of the large categories are called White Blood Cells, or Leukocytes. They can be stored in the Thymus, Spleen, Bone Marrow, Lymph nodes and they also float around in your blood.
Leukocytes can be further classified into phagocytes and lymphocytes. Phagocytes absorb and break down cells. Lymphocytes help recognize and remember foreign bodies.
- Neutrophils – most common and tend to attack bacteria
- Monocytes – largest type and do many things
- Macrophages – patrol for pathogens and also remove dead and dying cells
- Mast Cells – help with healing and pathogen defense
- B lymphocytes – produce antibodies and alert T cells
- T lymphocytes – destroy compromised cells and recruit other leukocytes
- Helper T cells – coordinate the immune response by recruiting cells and stimulating antibody production
- Killer T Cells – kill compromised cells
When an antigen enters the body, this is what occurs. Let’s assume this is a new, never before seen antigen. The antigen is going to be first recognized by a B lymphocyte, which will then learn the antigen and produce a marker protein that is specific to that antigen, called an antibody.
Antibodies are part of a family of chemicals called Immunoglobulins. They are typically titled Ig and a letter such as A,B,C (IgE for example). Different immunoglobulins are associated with different responses and antigens. They are then released to bind to the antigen, creating an immunocomplex. Because the antibody is now bound, it can be recognized by a T cell. The helper T cells can now recruit the appropriate leukocytes and killer T cells as needed.
Immune System Disorders
There are three main types of immune system disorders, however, we will only focus on one of those. That is what is called hypersensitivity.
Hypersensitivities, Allergies, and Allergic Reactions
Hypersensitivities can be categorized into four types. We will be focusing on type I, which in its most severe state can lead to anaphylaxis. In a type I hypersensitivity, the body is exposed to a new antigen. The body responds as it typically does, analyze the antigen and label it as either threat or no threat.
In food allergies, specific particles from the food get labelled as a threat. On the first exposure to this antigen, the body “primes” itself to launch an attack when the antigen is seen again. This causes the body to react to it as if it was a pathogen, triggering a vast immune response. The pathway goes like this:
The allergen particle gets identified and bound to it’s specific antigen, for a type I allergic reaction, it has to be what is called IgE mediated. This just means that it has to be triggered by an IgE antibody. The immunocomplex is then presented to the mast cells which triggers a release of a bunch of chemicals. There are a few that are released but the prominent one is histamine.
These chemicals cause the symptoms we typically associate with an allergic reaction this includes itching, redness, inflammation, and so on. Most reactions can be controlled using a drug such as Benadryl, which is an antihistamine drug. It binds to the histamine receptors to block them, reducing the allergic reaction. In more severe cases, the reaction progresses to what we call anaphylaxis.
In anaphylaxis, a few things occur:
- Shock – which leads to hypotension
- Bronchoconstriction – constriction of the airways
- Rash – usually an itchy one, such has hives
- Angioedema – where blood vessels swell, typically in the airway
For most people, shock means something similar to surprise, however, the medical definition is far from the same. Shock in medicine is defined the existence of hypoperfusion, which essentially means lack of blood flow. If untreated, this leads to organ failure and death, further complicating the situation. Shock can be onset in a number of ways, anaphylaxis being one of them.
Anaphylaxis is treated primarily with two drugs – Benadryl and Epinephrine (EpiPen). Epinephrine, or EpiPens are the rescue drug, where as Benadryl works over a longer period of time. The effects of Epinephrine can be seen within a few seconds of injection, however, it only last’s about 5 minutes.
Epinephrine works by constricting the blood vessels, which will temporarily increase blood pressure, allowing perfusion to occur easier. Additionally, it reduces the amount of angioedema, allowing an opening of the airway. Lastly, it causes brochodilation, the opposite of bronchoconstriction.