Everything you need to know about allergic reactions

The American Academy of Allergy, Asthma & Immunology estimates that 50 million Americans have some form of allergic disease, a condition that happens when your body’s immune system mounts a response to a substance that’s not actually a threat to you.

Here’s everything you need to know about allergic reactions, the 6th most common chronic illness in the U.S.

1) There are four types of hypersensitivity reactions

Not all allergic reactions are the same. In fact, they’re categorized into four different types.

Type I is anaphylaxis, an immediate response to an allergen that causes life-threatening airway swelling and sends the body into shock. Anaphylaxis typically happens seconds or minutes after exposure to the allergen.

Type II is called a cytotoxic reaction, where antibodies from your immune system bind to antigens on healthy cells, damaging or destroying those cells. Cytotoxic reactions typically lead to rapid destruction of blood cells, healthy tissue or vital organs, which can cause life-threatening complications.

Type III is known as an immune complex reaction, where immune cells bind together and deposit in blood vessels and organs, leading to serious complications.

Type IV is called a delayed hypersensitivity reaction, which usually causes a rash 12-48 hours after coming into contact with an allergen. Common examples of this type of reaction include rashes that result from contact with poison ivy, poison oak, nickel and latex.

2) You can develop a hypersensitivity at any point in your life

One of the reasons why allergic reactions can be perplexing to patients and health care providers is because it’s possible to develop a new allergy at any point in your life. This means even if you’ve taken a medication or eaten a food in the past without any adverse effects, you can develop a new allergy to it in the future.

3) Allergic reactions range from harmless to life-threatening

Some allergic reactions are limited, while others are life threatening. The severity of the reaction depends on which of the four types of hypersensitivity reactions it is, and the degree to which you’re allergic to the substance.

4) There are several treatment options for allergic reactions

For each type of hypersensitivity reaction, there are treatments to help reverse the reaction and mitigate the effects of it. Anaphylactic reactions require epinephrine (people who have had an anaphylactic reaction in the past should carry an EpiPen with them at all times.) Other hypersensitivity reactions are treated with steroids, immunomodulators and/or antihistamines.

5) Some allergens are more common than others

While in theory it’s possible to be allergic to nearly anything, in practice, some allergies are much more common than others. For instance, eight foods (cow’s milk, eggs, tree nuts, peanuts, shellfish, wheat, soy and fish) are responsible for the majority of food allergies. And antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) account for most medication-induced allergic reactions.