Anaphylaxis Causes and Triggers: Foods, Medications, Insect Stings

Anaphylaxis is a serious allergic reaction that usually involves multiple areas of your body at the same time.

It’s often characterized by breathing trouble, swelling in the face or other areas, and hives or other skin reactions. But anaphylaxis can involve a variety of symptoms, with none of them considered the defining feature.

An anaphylactic reaction happens when your immune system releases a large number of chemicals all at once, in response to what it perceives as a dangerous invading substance.

Like all allergic reactions, anaphylaxis happens when your immune system becomes sensitized to a specific allergen, such as a food, medication, or type of insect venom.

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A number of factors are likely to affect whether you become allergic to a substance, from your personal and family history of allergies to your history of exposure to the substance in question.

Ultimately, you can’t know why you became allergic to a substance that triggers anaphylaxis. But you can and should recognize what you’re allergic to, so that you can take steps to avoid exposure and treat anaphylaxis as soon as it occurs.

Certain groups of people are more likely to be sensitive to specific triggers of anaphylaxis, which may help you or your doctor figure out what’s causing your symptoms in unclear cases. (1,2,3)

What Causes Anaphylaxis?

Anaphylaxis is a particularly severe type of allergic reaction that happens when you experience numerous allergic symptoms at once.

Normally when you have an allergic reaction, your symptoms are confined to one area of your body, such as a skin rash or a runny, itchy nose. But in anaphylaxis, several different areas of your body react to the same allergen.

Understanding Anaphylaxis Risk

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You become allergic to an allergen by being sensitized to it with exposure. You can become allergic to a substance after you’ve been exposed to it only once, but an allergy can also develop after long-term or repeated exposure to a substance.

There’s no known way to predict when you might have an anaphylactic reaction to a substance that hasn’t triggered one in the past. You can have an anaphylactic reaction to something you already know you’re allergic to, or anaphylaxis may be the first sign that you’re allergic to a substance.

In an anaphylactic reaction, tissues in different parts of your body release chemicals as part of an immune system response. These chemicals cause the symptoms that, together, constitute anaphylaxis. (2,3,4)

Risk Factors for Anaphylaxis

A number of factors make it more likely that you’ll experience anaphylaxis, or an anaphylactic reaction to a specific allergen.

You’re more likely to experience anaphylactic reactions generally (but possibly not in response to all allergens) if you have a genetic predisposition to allergies and asthma, known as atopy.

You may also be more likely to experience anaphylaxis if you live in a northern rather than southern area of the United States; prescription rates for self-injectable epinephrine (the first-line treatment for anaphylaxis) are higher in the North.

And you’re more likely to develop anaphylaxis if you have asthma, cardiovascular disease, mastocytosis (a condition in which mast cells accumulate in your skin or internal organs), or a substance abuse disorder. (5)

If you’re taking a beta blocker or ACE inhibitor drug, any anaphylactic reaction you have to an allergen may be more severe.

The longer it’s been since your last exposure to an allergen, the less likely it is that you’ll have an anaphylactic reaction.

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When it comes to allergic reactions to drugs, oral drugs are less likely to cause anaphylaxis than drugs administered in a different way (injected, infused by IV, or delivered rectally or vaginally).

Drugs that you receive intermittently, rather than on a regular basis, are also more likely to cause anaphylaxis.

People with a higher income and higher education level are more likely to experience anaphylaxis, for reasons that aren’t completely clear.

Men are more likely to experience anaphylaxis in response to insect venom, while women are more likely to experience it from exposure to latex, aspirin, contrast medium (used for certain imaging scans), or muscle relaxants. (6)

Children are more prone to anaphylaxis caused by food triggers, while adults are more likely to get it from antibiotics, contrast medium, anesthetics, or insect venom. (3)

Common Anaphylaxis Triggers

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Anaphylaxis can be triggered by any allergen. The most common triggers of anaphylaxis include foods, medications, latex, and insect venom. (1)

While pollen and other airborne allergens are common causes of respiratory symptoms (hay fever or allergic rhinitis), they rarely cause anaphylaxis, according to the U.S. National Library of Medicine. (2)

Common anaphylaxis triggers can be found in the following categories.

Foods Widespread food triggers of anaphylaxis include:

  • Peanuts
  • Tree nuts
  • Fish and shellfish
  • Milk
  • Eggs
  • Soy
  • Wheat
  • Red meat

Drugs Medications that can cause anaphylaxis include:

  • Allergen extracts (used for allergy treatment)
  • Antibiotics
  • Antiserum drugs
  • Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs)
  • Benzocaine, administered topically
  • Blood and blood products
  • Enzymes, such as streptokinase
  • Hormones, such as insulin and progesterone
  • Monoclonal antibodies  (including biologic drugs) (7)
  • Opioids
  • Vaccines

Insect or Snake Venom Fire ants and bees, wasps, and hornets are the insects most likely to cause anaphylaxis when they bite. Snake bites are a less common trigger.

Other Triggers Latex, dialysis membranes, semen, contrast medium, and skin disinfectants can all cause anaphylaxis. (3)

Certain substances and activities can also trigger what’s known as an anaphylactoid reaction. This reaction isn’t allergic in the sense that your body is sensitized to an allergen, but the effects and treatment are virtually the same.

Some of the same triggers can cause either an anaphylactic or an anaphylactoid reaction.

Common triggers of an anaphylactoid reaction include:

  • Contrast medium
  • Aspirin and other NSAIDs
  • Opioids
  • Monoclonal antibodies
  • Exercise (8)

Since exercise isn’t a substance, it can’t be an allergen, but it does cause an anaphylactoid reaction in some people. This can happen with aerobic exercise like jogging or even walking.

You may be at greater risk for an exercise-induced reaction when you eat certain foods before exercising, or when the weather is particularly hot, cold, or humid. (4)

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