Anaphylaxis Causes and Triggers

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.

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.

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.

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.

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.

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

In some situations, such as reactions to drugs like penicillin, the longer it’s been since your last exposure to an allergen, the less likely it is that you’ll have an anaphylactic reaction if exposed again.

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.

Common Anaphylaxis Triggers

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 more commonly cause anaphylaxis include:

• Allergen extracts (used for allergy treatment)
• Antibiotics
• Antiserum drugs
• Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs)
• Blood and blood products
• Enzymes, such as streptokinase
• Monoclonal antibodies  (including biologic drugs)

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• 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.

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, especially aerobic exercise like jogging or walking

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