How to Treat an Allergic Reaction Caused by Food Allergies

“Being proactive is key…”

BY STEPHNIE @the Brimly Test Kitchen

February 27, 2025

Image Source/Maryam Sicard

15 minute Read

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FEATURE ARTICLE

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“An allergy is like a fire alarm—when it goes off, you must act fast and decisively.”
— Dr. Ruchi Gupta, Food Allergy Researcher and Author of Food Without Fear

Food allergies are a common health concern, and allergic reactions to food can range from mild discomfort to life-threatening emergencies. Knowing how to recognize and treat an allergic reaction quickly is crucial. This article discusses common food allergens, why allergic reactions occur, signs and symptoms from mild to severe, how to take action for mild reactions and for anaphylaxis (severe reactions, including the use of an epinephrine auto-injector), what to do after a reaction, and long-term strategies to manage and prevent food allergy reactions.

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Image courtesy of Maryam Sicard

What Are Food Allergies and Why Do They Occur

A food allergy is when the immune system mistakenly reacts to a harmless food protein as if it were a threat. The first time someone eats a particular allergenic food, their body may produce specific antibodies (IgE) against it. Upon subsequent exposures, those antibodies trigger immune cells to release histamine and other chemicals, causing the symptoms of an allergic reaction. Factors like genetics and environment play a role in who develops food allergies, but the underlying reason is that the immune system is overreacting to a normally safe food component.

Common Food Allergens

While any food could potentially cause an allergy, a small group of foods account for most allergic reactions. In many countries, the top eight allergens are:

Milk (dairy)
Eggs
Peanuts
Tree nuts (almonds, walnuts, cashews, pecans, etc.)
Fish
Shellfish (shrimp, crab, lobster, etc.)
Wheat
Soy

In some regions, sesame is also considered a major allergen (often included on labeling lists). People can be allergic to other foods as well. It’s important to know and avoid your specific trigger foods, because even a tiny amount of the allergen can potentially cause a reaction.

Symptoms of Food Allergies (Mild to Severe)

Food allergy symptoms can vary widely. They may affect the skin, digestive tract, respiratory system, or circulatory system (e.g. blood pressure). Some reactions are mild, while others can be life-threatening. Here are some examples of symptoms:

Mild symptoms: Itching, mild nausea or stomach discomfort, sneezing and runny nose, or a slight itchy feeling in the mouth.
Severe symptoms (anaphylaxis): Difficulty breathing (wheezing, shortness of breath), swelling of the throat, tongue, or lips; large areas of skin irritation or redness on the skin; repetitive vomiting or severe diarrhea; dizziness, fainting, or a sudden drop in blood pressure (shock).

Any symptom that involves breathing trouble or feeling faint indicates a severe reaction. Also, having several mild symptoms at the same time can mean the reaction is becoming severe. When in doubt, treat it as severe and get emergency medical help.

Video courtesy of Michigan Medicine

This video “Food Allergy Explained: Basics, Back to School & Beyond” by Michigan Medicine provides an evidence-based overview of food allergies, covering signs and symptoms, how to recognize and treat allergic reactions (including the use of epinephrine auto-injectors), and strategies for avoiding allergens. It also discusses navigating food allergies in school settings, coping with anxiety related to allergies, and emerging treatments like oral immunotherapy. The video emphasizes preparedness, communication, and ongoing medical management to ensure safety and quality of life for individuals with food allergies.

Immediate Treatment for Mild Allergic Reactions

If an allergic reaction is mild, you can often manage it at home with the following steps:

Stop eating the suspected food: Remove the offending food immediately. Have the person spit out and rinse their mouth if any remains, to clear away the allergen.
Give an antihistamine: An over-the-counter antihistamine can help relieve mild symptoms like itching or sneezing. Use the correct dose as directed on the package or by a doctor.
Monitor the person closely: Have them rest and stay calm. Watch to ensure the symptoms are improving, not worsening. Continue to observe for at least an hour or two, and make sure someone stays with the person during this time.
Be ready to seek further help if needed: If symptoms begin to worsen or new symptoms appear, treat the situation as a severe reaction. That means using epinephrine and calling emergency services.

Even if the mild symptoms start to improve, always err on the side of caution. If you’re unsure whether the reaction is truly mild, or if the person feels uneasy, seek medical advice – it’s better to be safe than sorry and have a medical professional evaluate the situation if there's any doubt.

Emergency Response for Severe Allergic Reactions (Anaphylaxis)

A severe allergic reaction (anaphylaxis) is life-threatening and requires immediate action:

Inject epinephrine immediately: Use an epinephrine auto-injector at the first sign of a severe reaction (such as difficulty breathing, throat swelling, or any rapid-onset serious symptoms). Inject it into the outer mid-thigh muscle, as instructed by the device.
Call emergency services (911): Do this right after giving the epinephrine (or have someone call while you administer it). Tell the dispatcher that the person is having a severe allergic reaction and that epinephrine has been given.
Lay the person down (if possible): Have them lie on their back and elevate their legs to help prevent shock. If they are having trouble breathing, let them sit up slightly – whatever position makes breathing easier. Avoid sudden standing or walking, as it could lead to a dangerous drop in blood pressure.
Monitor and assist breathing: Loosen any tight clothing. Stay with the person and keep them calm. Watch their breathing and alertness. If they vomit, turn them on their side to prevent choking. If they lose consciousness and stop breathing, begin CPR if you are trained to do so.
Give a second dose of epinephrine if needed: If the person isn’t improving within about 5 minutes and help hasn’t arrived yet, use a second epinephrine auto-injector (if available).
Ensure they get to the hospital: Even if the epinephrine seems to have helped and the person feels better, they still need medical evaluation. A healthcare professional should observe them in case of a biphasic reaction (where symptoms return after a few hours). Paramedics will usually transport the person to the emergency room for further treatment and monitoring.

Taking quick action is very important during anaphylaxis. Using an epi-pen promptly and calling for help can save a life. Never hesitate to give epinephrine if you suspect a severe allergic reaction.

Image courtesy of Getty Images

What to Do After an Allergic Reaction

After handling the immediate emergency, there are important follow-up steps to ensure the person recovers well and to reduce the risk of future incidents:

Medical evaluation: Severe reactions require observation at the hospital to ensure symptoms don’t return; even if a reaction is mild and handled at home, it’s wise to inform your doctor about it.
Follow up with an allergist or doctor: It’s good to have a medical follow-up after an allergic reaction, especially if it was a first-time reaction or you aren’t completely sure what caused it. An allergist can help identify the offending food (possibly through allergy tests) and update your treatment plan. Also, be sure to replace any medications that were used during the reaction (for example, get a new epinephrine auto-injector if one was used).
Review and update your allergy action plan: Think about how the reaction happened and what could be learned. Make any necessary changes to prevent a repeat (such as being more vigilant about label reading or asking about food preparation when dining out). Ensure that friends, family, or caregivers are informed of the allergy and know what to do in an emergency.

Image courtesy of Getty Images

Long-Term Management and Prevention of Food Allergies

Managing a food allergy is an ongoing process. Key strategies for long-term management (and preventing allergic reactions) include:

Avoid the allergen completely: Strict avoidance of the problem food is the primary way to prevent reactions. Read ingredient labels on foods every time. Be careful about cross-contamination in the kitchen. When dining out or eating at someone else’s home, inform them about your allergy so they can help you avoid the ingredients.
Always carry your emergency medicine: If you have a known food allergy, keep your epinephrine auto-injector with you at all times. Consider carrying two injectors in case an extra dose is needed, and also make sure your injectors are not expired.
Wear medical identification and inform others: Consider wearing a medical alert bracelet or necklace that lists your allergy, which can speak for you in an emergency. Make sure the people around you (friends, family, teachers, coworkers) are aware of your food allergy. Teach them what to do if you have a reaction, including how to use your epinephrine auto-injector if you need assistance.
Have an action plan and share it: Work with your doctor to write down an Allergy Action Plan. This document should outline what symptoms to watch for, when to give epinephrine, and who to call in an emergency. Share your plan with those who might need to assist you (for example, your child’s school or daycare should have a copy).
Regular medical follow-up: Have periodic check-ups with an allergist. Some allergies (especially in children) may be outgrown, so re-testing might be advised. Your doctor can also inform you of any new therapies that might help.

Image courtesy of Getty Images

The Bottom Line:

Living with food allergies means staying vigilant, but with careful management, you can lead a healthy life. By consistently avoiding your allergen and being prepared to treat accidental exposures, you can prevent most allergic reactions and confidently manage your condition.

Being proactive is key—read labels, communicate your allergies clearly when eating out, and always carry your emergency medication. Educate those around you so they can support you in case of an emergency, and stay updated on new treatments and strategies with regular check-ins with your allergist. While food allergies require extra caution, they don’t have to control your life. With the right precautions, you can continue to enjoy food safely and live without fear.