Some foods can cause delayed reaction. This most often happens in infants who have Food Protein-Induced Enterocolitis Syndrome (FPIES), sometimes referred to as a delayed food allergy. According to the American Academy of Allergy, Asthma and Immunology website, “FPIES is a severe condition causing vomiting and diarrhea. In some cases, symptoms can progress to dehydration and shock brought on by low blood pressure and poor blood circulation.”₁

Delayed reactions to peanuts are uncommon but they can occur in rare instances. In fact, delayed reactions caused by FPIES can happen to any food and usually don’t start until hours after a food is eaten.  “FPIES allergic reactions are triggered by ingesting a particular food. Although any food can be a trigger, the most common culprits include milk, soy, and grains.”₁ Visit AAAAI website to learn more about FPIES here.

In addition to delayed food reactions, there are also immunoglobulin E

(IgE) mediated reactions. If you have an allergy, your immune system overreacts to an allergen by producing antibodies called Immunoglobulin E (IgE).₂ For the approximately 1% of people with a peanut allergy, reactions can be serious and potentially life-threatening. Preventing accidental ingestion and avoiding reactions requires consistent and ongoing management. When an individual with IgE mediated food allergy accidentally eats a food that contains their offending allergen (e.g. peanut), a reaction will usually happen within minutes, but can take up to 2 hours.

Anaphylaxis often begins within minutes after a person eats a problem food. Less commonly, symptoms may begin hours later. Up to 20 percent of patients have a second wave of symptoms hours or even days after their initial symptoms have subsided. This is called biphasic anaphylaxis.₃

If you have a peanut allergy, your body will work double-time to protect itself from the protein in peanuts that will cause an immune reaction in your body. This is what happens when you have an allergic reaction. The symptoms that occur when your body is in “attack mode” can range from hives to nausea and facial swelling to anaphylaxis. The range of these symptoms can be from mild to life threatening.₄ It is important to note that a delayed biphasic reaction seem to be tied to the severity of the initial anaphylactic reaction.₅

If you have a peanut allergy, make sure you are always prepared for a reaction by keeping your epinephrine near you at all times. This medication can reverse the symptoms of an anaphylactic reaction, but you have to use it quickly for it to be effective. Any time epinephrine is used, it is important to seek emergency medical attention in case a second round (biphasic) reaction happens, which may require more intensive medical intervention.

You should always consult a board-certified allergist if you have concern about a food allergy. Working with an allergist who is familiar with your health history will assist in managing a food allergy risk.

References:

1. Moore, A. M. (2020, September 28). Food Protein-Induced Enterocolitis Syndrome: AAAAI. American Academy of Allergy, Asthma & Immunology. https://www.aaaai.org/conditions-and-treatments/library/allergy-library/food-protein-induced-enterocolitis-syndrome
2. (n.d.). IMMUNOGLOBULIN E (IGE) DEFINITION. AAAAI. American Academy of Allergy, Asthma & Immunology. https://www.aaaai.org/conditions-and-treatments/conditions-dictionary/immunoglobulin-e-(ige)
3. Kemp SF. (2008). The post-anaphylaxis dilemma: How long is long enough to observe a patient after resolution of symptoms?
   nlm.nih.gov/pubmed/18377774
4. Types of allergies: Food allergy. (n.d.). acaai.org/allergies/types/food-allergies
5. Alqurashi W, et al. (2015). Epidemiology and clinical predictors of biphasic reactions in children with anaphylaxis. DOI:10.1016/j.anai.2015.05.013

Though it’s increasingly in the national discourse, the fact is less than 1% of Americans have a peanut allergy,* and food allergies only affect about 5% of children and 4% of teens and adults.** Peanut allergies are not the most common, but they are among the top eight food allergens, and reactions to food allergens can be serious and sometimes life-threatening.

Researchers believe that food allergies are on the rise, but no one knows what causes food allergies in some people and not in others. While several hypotheses are being investigated, certain conditions in infants, including severe eczema and egg allergy, are known to be risk factors for developing a peanut allergy.* Vaccines are not considered a cause of peanut allergy, and the Center for Disease Control and Prevention clearly states that peanut oil is not used in vaccines.**

^* http://www.niaid.nih.gov/topics/foodallergy/clinical/documents/faguidelinesexecsummary.pdf

Yes. Research shows that introducing peanut foods to infants reduces their likelihood of developing peanut allergies.* Guidelines from the National Institute of Allergy and Infectious Diseases recommends that parents introduce infant-appropriate peanut foods starting as early as 4-6 months, depending on their risk for developing peanut allergy.** Discuss questions about food allergies and introducing peanut foods with your pediatrician or healthcare provider.

No. The American Academy of Pediatrics explicitly states that research does not support avoiding any food as a means of preventing food allergies. They also state that there’s no need for women to avoid peanuts while pregnant or breastfeeding, unless they are allergic.*

Diagnosing a food allergy is complex, and should be conducted by a board-certified allergist. Blood and skin-prick tests are valuable tools for identifying an allergy, but are not conclusive in diagnosing food allergies on their own. Oral food challenges are the gold standard for food allergy diagnosis.*

Avoiding a food allergen is the only way for allergic individuals to prevent a reaction.* Those who are food allergic should always check labels on packaged foods, ask about ingredients in meals at restaurants, and have an emergency action plan in place in case of accidental exposure.

Identifying and treating a reaction quickly is paramount for safety. Common signs and symptoms of food allergy reaction include:*
– hives
– itching and swelling of the mouth, throat and eyes
– vomiting and diarrhea
– difficulty breathing
– reduced blood pressure, weakness, and fainting

Anaphylaxis is a life-threatening allergic reaction, and can occur when only a small amount of the allergenic protein is eaten. Epinephrine is the approved treatment for anaphylaxis and should be administered without delay.* Individuals should seek medical help when a reaction occurs, including calling 911 anytime epinephrine is administered.

No. Research does not support skin contact or airborne peanut butter exposure as a source of anaphylaxis, though hay fever type reactions may occur.* Most instances of anaphylaxis are the result of accidental ingestion of peanut proteins, or exposure through the eyes or mouth.

Common household cleaners have been demonstrated to be effective in removing peanut proteins from surfaces and eating areas. Soap and water remove peanut proteins from skin, but sanitizer alone does not.*

No. To the contrary, research has shown that banning peanuts in schools may increase the risk for reactions and does not reduce the frequency of epinephrine use.*,** Bans give a false sense of security, and are not recommended by healthcare professionals. Best practices for managing food allergies in foodservice include using basic food safety techniques, separating allergens, clearly labeling allergens and avoiding cross contact in kitchens and serving areas. Most importantly, allergic customers should use caution when dining out, be sure to notify staff of their allergy and be prepared in case of accidental ingestion.

From 1997 to 2007, the prevalence of all reported food allergies has increased by 18 percent among children, according to Food Allergy Research & Education (FARE). A FARE-funded study found the number of children in the U.S. with peanut allergy more than tripled between 1997 and 2008. No one knows the real reason why, but scientists have a variety of theories.