Food Allergy vs. Food Sensitivity (Food Intolerance) vs. Food Poisoning

Many people are convinced that they have food allergies.  For some, this is a correct assumption.  For others, they may actually have a food sensitivity or food intolerance, but not a true food allergy.  Still others, may have an episode of food poisoning.  In order for it to be a true food allergy, there must be a specific immune response to a particular food protein involving the immunoglobulin E (IgE) antibody (also known as the “allergy” antibody).  This type of reaction is called a Type I, IgE-mediated immunologic reaction.  The symptoms of a food allergy usually occur within seconds to a couple of hours after exposure to a food.


A food sensitivity or food intolerance, on the other hand, is a non-immune toxic reaction against a food.  Unlike food allergies, the reaction usually occurs in a delayed fashion and typically develops between 1 hour and 3 days after eating the food.  It carries a much lower risk and is not as serious.  The food can affect different people in different ways.  Any organ system can be affected.  Since it can take days to develop symptoms, people with food sensitivities are difficult to diagnose and may go undiagnosed for many years.  One of the best ways to determine if someone has a food sensitivity is to do a food elimination diet and then add one food at a time back for several days to see if their symptoms re-occur.  If it does, then the individual should remove that food from their diet.  Some examples of food sensitivities and their cause are as follows:

  1. Gluten Intolerance – Inability to digest gluten (wheat, rye, and/or barley) or more recent research suggests that it may be the inability to digest FODMAP’s (Fermentable Oligo-, Di-, Mono-saccharides and Polyols) rather than gluten.
  2. Lactose Intolerance – Deficiency of the enzyme “lactase” which normally breaks down the sugar lactose found in milk products.
  3. Favism (Glucose-6-phosphate dehydrogenase deficiency or G6PD deficiency) – Genetic deficiency in the enzyme G6PD causes anemia, fatigue, abdominal pain, headache, fever, etc. when these individuals eat fava beans or take certain medications (i.e., sulfonamides, certain anti-malarial drugs, aspirin, nitrofurantoin, dapsone, isoniazid).
  4. Adverse Reactions to Preservatives and/or Food Dyes – Some examples include sulfites, tartrazine, sodium benzoate, nitrates, nitrites, parabens, monosodium glutamate (MSG), aspartame, and butylated hydroxytoluene (BHT).
  5.  Pharmacologic Effect of Food – Some examples of chemicals found in a variety of foods include caffeine, tyramine, and histamine.


Food poisoning can mimic the symptoms of food allergies or food sensitivities.  Typically these symptoms of food poisoning can include diarrhea, abdominal pain, nausea, and/or vomiting.  Other symptoms more consistent with food poisoning than that of either food allergies or food sensitivities include fever, bloody diarrhea, blood in vomit, and/or general weakness.  The symptoms of food poisoning generally begin from a few hours to a few days after eating the affected food.  They typically last hours to a few days, but can last longer.  Often, other individuals eating the same food will exhibit similar symptoms which make the diagnosis of food poisoning more likely.  The causes of food poisoning most often include contamination with various bacteria, viruses, or parasites.  Other causes can include natural toxins (found naturally in many plants and some fish, etc.), other toxins that can arise from certain bacteria and fungi, and prions.  It is always highly recommended to wash one’s hands thoroughly before eating and avoid eating undercooked or raw meat, poultry, fish, shellfish, sprouts, or eggs  however, many cases of food poisoning are caused by poor sanitary conditions, spoilage, and/or improper food processing and/or storage of the food.  Travelers should also be extremely careful.  When in other countries, particularly third world countries, it is highly recommended to drink sealed bottled water, avoid ice and any food that has been washed or mixed with the local water (unless boiled and filtered), and avoid unpasteurized foods.  Dehydration is one of the most serious complications from a case of food poisoning.  It does not take long for a patient who has severe vomiting and/or diarrhea to become dehydrated.  It is therefore important to drink plenty of fluids in cases of food poisoning.  If symptoms last 2-3 days, one should seek medical care, so that the physician can obtain an appropriate history and perform a thorough physical examination.  The physician will order the appropriate blood work and obtain stool samples and cultures.  Treatment may include intravenous fluid and electrolyte replacement as well as antibiotics or anti-parasitic medication, if needed.

Note:  There is a food poisoning that can mimic an allergic reaction called “Scrombroid poisoning.”  The symptoms of this illness can include flushing and rash, rapid heart rate, lightheadedness/dizziness, headache, nausea, abdominal pain, and/or diarrhea.  In severe cases, one may experience shortness of breath, wheezing, swelling of the throat or tongue, and/or decreased blood pressure which can be life-threatening.  These symptoms all are typical of an allergic reaction, however, in scrombroid poisoning, there is no allergy and there is no contamination with bacteria, viruses, or parasites.  The cause of this condition is a chemical called histadine that is naturally occurring in some fish (i.e., tuna, bluefish, mahi mahi, mackerel, sardines, herring, anchovies).  When the fish is not properly stored, the fish spoils and certain bacteria grow and cause the histadine to convert to histamine.  It is the histamine (which is one of the main culprits in causing allergic reactions), that is the cause for the allergic symptoms found in scrombroid poisoning. Treatment of mild symptoms can be treated with antihistamines, however, if symptoms become more severe or they become prolonged, one should go to the closest emergency room for treatment.



The symptoms of food allergies can be diverse.  Some of the more common symptoms found with food allergies include:  generalized itching (pruritus), itchy mouth and/or throat, hives (urticaria), other rashes, abdominal pain, diarrhea, vomiting, wheezing, shortness of breath, swelling (angioedema) , throat tightening, and/or anaphylaxis.  As mentioned above, the symptoms usually occur within seconds to a couple of hours after exposure to the food.  They can be very mild or very severe and life threatening.  The most common foods associated with life-threatening reactions from foods include:  peanuts, tree nuts, fish, and/or shellfish.

Most Common Food Allergies:

The most common food allergies in infants and children are milk, egg, soy, wheat, peanuts, and tree nuts. In adults, the most common food allergies are fish, shellfish, peanuts, and tree nuts.  It should be noted that anyone can be allergic to any food.  That food can cause symptoms ranging from very mild to very severe life-threating reactions.

Food protein-induced enterocolitis syndrome (FPIES):

Food protein-induced enterocolitis syndrome is a type of food allergy which usually affects infants and babies.  The cause of the syndrome is usually due to a food, most commonly cow’s milk formula and soy-based formula.  Breast milk may also contain food proteins that can cause this condition, however, this is rare.  Other foods commonly associated with this syndrome can include oats, rice, sweet potatoes, squash, chicken, turkey, peas, green beans, and fish.  Symptoms include vomiting and diarrhea (occasionally with blood), dehydration, weight loss, and failure to thrive.  It is typical, however, for the symptoms to begin several hours after the food is consumed.  This delay in symptoms makes it more difficult for this condition to be diagnosed.  The diagnosis is further complicated by the fact that usual skin and blood testing done for food allergies usually are not be positive.  Once the diagnosis is established, the food should be eliminated from the infant’s diet and alternative foods should be consumed.  It is usually necessary to see a board certified allergist to diagnose this often “difficult to diagnose” problem.

Diagnosis and Treatment:

If one suspects food allergies, one should seek a board certified allergist.  The allergists at Black & Kletz Allergy have had over 50 years of experience in diagnosing and managing food allergies and sensitivities in the Washington, DC, Northern Virginia, and Maryland metropolitan area.  Food allergies can be diagnosed by a thorough history and physical examination along with prick skin testing and/or blood testing. The management varies but in most instances, avoidance of the food is the recommended treatment.  If you feel that you may e an issue with food allergies or sensitivities, we would be happy to see you in one of our 3 convenient locations with offices in Washington, DC, McLean, VA (Tysons Corner, VA), and Manassas, VA.  Please feel free to call our office or alternatively, you may click Request an Appointment and we will respond within 24 hours on the next business day. Black & Kletz Allergy is proud to provide quality allergy and immunology care in a relaxed caring environment.