Medically reviewed on May 17, 2023 by Jillian Foglesong Stabile, MD, FAAFP. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.
Table of contents
Certain foods can trigger a unique response from your immune system, depending on your body composition.  Typically, those with a family history of allergic diseases are more likely to develop food allergies and adverse reactions.  These can include, but are not limited to, abdominal pain, hives, rashes, or blocked airways. 
Once these allergy symptoms are triggered, there’s no definitive answer about how long the reaction may last.3 However, a more severe reaction—such as anaphylaxis—can take hours or days to resolve and may become life-threatening if untreated. 
To better understand your food allergy and its long-term impact, we’re exploring what you need to know about intolerances to certain foods and their effects on the body.
Food allergies can develop when the body comes in contact with or consumes an allergen, in this case, the offending food. When this occurs, an antibody called immunoglobulin E (IgE) is created by the immune system and dispersed into the blood, which attaches itself to immune cells. 
Typically, the body’s first encounter with the allergen will not cause an allergic reaction. However, repeat contact with the allergen allows the IgE to recognize it and initiate an immune response against it later on. 
The severity of this response will differ depending on the individual. Scientists are still investigating the complete reasoning behind an allergic reaction. For example, are food allergies genetic? While it’s clear that genetics play some role, researchers have also identified a relationship between naturally occurring gut bacteria and an increased risk of developing food allergies. 
A family history of allergies unrelated to food may also predispose you to food allergies. These can include: 
While most food allergy reactions are triggered by an antibody called IgE, the level of IgE helps predict the type of reactions your body will have.
To better understand food allergic reactions, take a look at the three types of food allergies according to the level of IgE: 
How long does a food allergy reaction last? In mild cases, a food allergy will last only a few hours. In more severe cases, such as anaphylaxis, symptoms may persist for several days.
Anaphylaxis is an acute allergic reaction that can take effect seconds or minutes after ingesting an allergen. While it’s common in food allergies, it may also occur due to allergies to other things, such as bee stings.
When your body identifies this harmful invader, the immune system goes into overdrive to release a surge of chemicals throughout the body, including histamine, which triggers the body’s inflammatory response. 
These chemicals are what cause the symptoms of an allergy reaction. As they’re dispersed throughout the body, the blood vessels widen, and the muscles contract. This can cause blood pressure to drop, airways to narrow, and may cause you to have trouble breathing. Some may also experience a weak pulse, rash on the skin, and nausea. 
Allergy treatment involves an injection of epinephrine, also known as adrenaline, which can help relax the airway muscles to improve breathing. If you experience anaphylaxis or these symptoms, it’s critical to visit an emergency room as soon as possible so a healthcare provider can continue to monitor your condition. In some cases, symptoms can last for a few days. However, most often they’ll dissipate in a few hours following allergy treatment. 
Depending on the severity of your food allergy, reactions can last from a couple of hours to a few days. That said, it’s vital to understand what types of allergens may trigger a potentially life-threatening response.
The at-home Food Allergy Test from Everlywell measures your body’s IgE reactivity to common food allergens, such as almonds, cow’s milk, egg white, egg yolk, peanut, shrimp, soy, tuna, and wheat. Once your results are processed, an Everlywell healthcare provider will contact you to help you take steps toward a healthier you.