Anaphylaxis can be triggered by foods, medications, insect stings, latex, exercise, and in some cases, no identifiable cause at all. Food allergies are the most common trigger in children, while medications and insect stings account for a larger share of cases in adults. Roughly 6% of adults and 8% of children in the United States have a food allergy, and any allergic reaction has the potential to escalate to anaphylaxis under the right conditions.
Food: The Most Common Trigger
Nine foods account for about 90% of all food-allergic reactions in the U.S.: milk, eggs, peanuts, tree nuts (almonds, walnuts, pecans), fish (bass, flounder, cod), shellfish (crab, lobster, shrimp), wheat, soybeans, and sesame. Of these, peanuts and tree nuts are the most frequent causes of severe, life-threatening food reactions. Children are more likely to react to milk, eggs, and peanuts, while adults more commonly develop new allergies to shellfish and fish.
More than 160 foods can technically cause allergic reactions, but those nine dominate the statistics. Sesame was added to the major allergen list in 2021 after the FASTER Act recognized its growing role in allergic reactions. If you have a known food allergy, even trace amounts of the trigger food can set off a full anaphylactic response, which is why federal labeling laws require these allergens to be clearly listed on packaged foods.
Medications That Trigger Reactions
Antibiotics are the most common drug class to cause anaphylaxis. Penicillin and related antibiotics are responsible for the largest share of these reactions, though any antibiotic can potentially be the trigger. Chemotherapy drugs and monoclonal antibodies (a type of targeted therapy used for cancer and autoimmune conditions) have also emerged as significant causes.
Pain relievers like aspirin and ibuprofen, part of the NSAID family, can cause reactions ranging from hives and nasal congestion to, in rare cases, full anaphylactic shock. People with asthma or nasal polyps face a higher risk of NSAID sensitivity. Other drug classes linked to anaphylactic reactions include anti-seizure medications and ACE inhibitors, a common type of blood pressure medication.
Drug reactions can be tricky because they sometimes occur after you’ve taken the same medication safely before. Sensitization can build over multiple exposures, meaning the first few doses cause no problems while a later dose triggers a severe reaction.
Insect Stings and Venom
Stings from insects in the Hymenoptera order are a major cause of anaphylaxis, particularly in adults who spend time outdoors. The primary culprits are honeybees, yellow jackets, wasps (including the European paper wasp), hornets, and fire ants. Yellow jackets are among the most common allergy-triggering species in North America and Europe.
The venom from each species contains different proteins, which matters for treatment. Someone allergic to honeybee venom may not react to yellow jacket venom, and vice versa. Accurate identification of the insect that caused a reaction is important because venom immunotherapy (a long-term treatment that gradually builds tolerance) is species-specific. Most people who have severe sting reactions will react again if stung by the same type of insect in the future.
Latex Exposure
Natural rubber latex, found in gloves, balloons, rubber bands, and some medical devices, can cause anaphylaxis in sensitized individuals. Healthcare workers are at the highest risk because of repeated glove exposure. An estimated 8 to 12% of healthcare workers are latex-sensitive. Between 1988 and 1992 alone, the FDA received over 1,000 reports of adverse reactions to latex, including 15 deaths.
The shift toward non-latex gloves in hospitals and clinics has reduced new cases significantly, but latex allergy remains a concern for people who were sensitized years ago. People with latex allergy also sometimes react to certain foods, including bananas, avocados, chestnuts, and kiwi, because these contain proteins structurally similar to those in latex.
Exercise-Induced Anaphylaxis
Exercise-induced anaphylaxis is rare but can occur at any level of physical exertion, from a light jog to intense training. In many cases, exercise alone isn’t enough to cause a reaction. Co-factors that lower the threshold include eating certain foods before working out (particularly wheat or shellfish), cold exposure, drinking cold beverages, alcohol, NSAIDs, and possibly emotional stress.
This means someone might eat shrimp dozens of times with no problem and exercise dozens of times with no problem, but combining the two within a few hours triggers anaphylaxis. The unpredictable nature of these episodes makes them particularly difficult to manage. People diagnosed with this condition typically learn to avoid eating for several hours before exercise and to carry epinephrine.
Idiopathic Anaphylaxis: No Known Cause
In some cases, anaphylaxis occurs repeatedly with no identifiable trigger despite thorough testing. This is called idiopathic anaphylaxis. It’s a diagnosis of exclusion, meaning doctors rule out every known cause before applying the label. The episodes are real and equally dangerous. They produce the same symptoms and require the same emergency treatment as any other form of anaphylaxis.
What Makes a Reaction More Severe
Certain factors don’t cause anaphylaxis on their own but can make a reaction worse or harder to treat once it starts. Asthma is one of the most significant risk factors for fatal anaphylaxis, especially when it’s poorly controlled. The airway inflammation already present in asthma compounds the breathing difficulties that anaphylaxis causes.
Beta-blockers, a class of medication commonly prescribed for high blood pressure, heart conditions, and anxiety, pose a double problem. They may increase both the likelihood and severity of anaphylaxis by affecting how cells release inflammatory chemicals. On top of that, beta-blockers interfere with epinephrine, the primary rescue medication for anaphylaxis. They block the receptors that epinephrine targets in the lungs and heart, meaning the standard dose may not work as well. This makes prompt, appropriate epinephrine use even more critical for people on beta-blockers.
How Anaphylaxis Presents
Anaphylaxis typically develops within minutes to several hours after exposure to a trigger. It almost always involves the skin or mucous membranes: hives, flushing, itching, or swelling of the lips, tongue, or throat. A reaction is classified as anaphylaxis when these skin symptoms appear alongside at least one of two serious developments: breathing problems (wheezing, shortness of breath, stridor) or a dangerous drop in blood pressure (causing dizziness, fainting, or loss of consciousness).
Not every allergic reaction becomes anaphylaxis. The distinction matters because anaphylaxis is a medical emergency that requires epinephrine, while a mild allergic reaction (a few hives, minor itching) may resolve on its own or with an antihistamine. The challenge is that mild reactions can escalate quickly and unpredictably, sometimes within minutes.