Allergic reactions to food occur when your immune system mistakes a food ingredient, usually a protein, for something harmful and creates a defensive reaction to fight it. Only 2 percent of adults and 6 percent of children have a true food allergy. Most of the time, the reaction is not a true allergy but intolerance to the food or an inability to digest it properly.
The most common types of foods that trigger true allergic reactions are peanuts; tree nuts like walnut, pecans, cashews, and almonds; fish; shellfish; milk; eggs; soy products; wheat; and sesame seeds.
With good self-care, you can learn to avoid foods that trigger your symptoms or treat a reaction if you have one.
Symptoms of a food allergy usually occur quickly (30 to 60 minutes after eating or being exposed to the food). It may take only a small amount of the food to trigger a reaction. Your reaction can range from mild to severe.
Common symptoms of an allergic reaction are:
- Itchy mouth and lips
- Rash or hives
- Itchy skin
- Shortness of breath or wheezing
- Chest pain
- GI symptoms (nausea, vomiting, and diarrhea)
- Throat swelling
- Anaphylaxis – a severe reaction, usually with swelling of the face and throat, rapid heartbeat, and drop in blood pressure that may lead to collapse
It is important to determine if you have a food allergy or intolerance. The first step is to ask you questions about your medical history and to do a physical exam. This will help determine what additional allergy tests to perform and how to interpret the test results.
To better understand what may be triggering symptoms, we may ask that you:
- Keep a food diary. We may ask that you keep a careful record of what you eat, in order to help determine which foods are causing your symptoms.
- Try an elimination diet. By taking certain foods out of your diet one at a time, and seeing if this improves your symptoms, you can help us to diagnose food allergies. In severe food allergies, elimination diets are generally supervised by your doctor directly.
If additional allergy tests are needed, they may include:
- Prick/puncture skin testing. During this test, the skin of your arms or upper back will be pricked with small amounts of the suspected food source placed onto your skin. If the antibodies to the food are located under your skin, an allergic reaction will occur, causing a raised, red itchy area. This test takes about 20 minutes.
- Blood tests. RAST (Radioallergosorbent tests) are allergy tests that are done using a sample of your blood to identify possible antibodies to foods. These tests are not as sensitive as the prick/puncture skin tests, but they are easier to perform and safer for patients with severe symptoms.
Avoiding the food that triggers symptoms is the most effective way to treat your food allergy, but that may be challenging to accomplish.
Here are some tips to consider:
- Learn to read food labels. You can look for the ingredients that may cause your allergy. Avoid foods that are made in a facility that processes the foods you are allergic to.
- Prepare safe meals at home. If you read food labels carefully, and focus on fresh ingredients such as fruits and vegetables, you will be more likely to avoid problem foods.
- Exercise care when eating in restaurants. When you dine out, ask your server if the food ingredients you are allergic to (like peanuts or shellfish/fish) are used in the kitchen. There could be cross-contamination with the food served to you.
- Check ingredients in items other than food. Be aware that the food ingredients that cause your allergies may be present in other items, such as toys or cosmetics. Avoid them as much as possible.
- Don't share utensils or kiss anyone who has eaten a problem food. Saliva may contain the food ingredient that causes your reactions, so you will need to be careful kissing or sharing food utensils.
- Carry antihistamines with you at all times. Liquid Benadryl or Zyrtec (cetirizine) are good antihistamines to treat mild allergic reactions. They can be readily absorbed, and you can adjust the dose easily.
- Carry and use an EpiPen® for severe reactions. Since it is impossible to completely avoid a food ingredient that you are allergic to, you may be prescribed an EpiPen® containing epinephrine. Keep your EpiPen® with you at all times so that you can self-inject if you are exposed to a trigger food.
If you have an emergency medical condition, call 911 or go to the nearest hospital.
An emergency medical condition is any of the following:
(1) a medical condition that manifests itself by acute symptoms of sufficient severity (including severe pain) such that you could reasonably expect the absence of immediate medical attention to result in serious jeopardy to your health or body functions or organs; (2) active labor when there isn't enough time for safe transfer to a Plan hospital (or designated hospital) before delivery, or if transfer poses a threat to your (or your unborn child's) health and safety, or (3) a mental disorder that manifests itself by acute symptoms of sufficient severity such that either you are an immediate danger to yourself or others, or you are not immediately able to provide for, or use, food, shelter, or clothing, due to the mental disorder.
This information is not intended to diagnose health problems or to take the place of specific medical advice or care you receive from your physician or other health care professional. If you have persistent health problems, or if you have additional questions, please consult with your doctor. If you have questions or need more information about your medication, please speak to your pharmacist. Kaiser Permanente does not endorse the medications or products mentioned. Any trade names listed are for easy identification only.