What are the symptoms of food allergies?

Jill A. Grimes, MD
Family Medicine
You will know you have a food allergy if you have signs and symptoms within minutes to a couple hours after exposure to even small amounts of the offending protein. Signs of food allergies include itchy, red rashes; swelling; flushing; nausea; abdominal cramping and diarrhea; stuffy nose; wheezing; racing heart; and metallic taste in your mouth.

Your doctor will diagnose a food allergy mainly by history, combined with either skin or blood testing for more accuracy. Skin testing can be helpful, but there are many false-positives, which means the test says there is an allergy, but there is not. Negative results on a skin test, however, are very accurate that there is no food allergy, so that can be very reassuring. Blood tests are also poorly predictive, being accurate only roughly half of the time. However, high levels of blood tested antibodies are very suggestive of an allergy to that food.

If you think you may have a true food allergy, discuss it with your doctor and consider additional testing before permanently restricting your diet. 
Dr. Mark Hyman, MD
Family Medicine
Symptoms of delayed food allergies can include brain fog, fatigue, weight gain, depression, digestive issues, joint and muscle pain, and more. Watch functional medicine expert Mark Hyman, MD, describe common but subtle symptoms of food sensitivities.
True food allergies are caused by immune system reactions. Most reactions occur within five minutes to one hour after eating the food. Symptoms can be mild such as hives (red, raised, itchy patches of skin), swelling, itchy/watery eyes, and runny nose or sneezing. Severe symptoms (also called anaphylaxis) can include throat swelling, difficulty breathing, vomiting or diarrhea, feeling dizzy and passing out. Sometimes severe reactions that are not treated quickly can even lead to death. Symptoms can vary from person to person and can even change with different times a person has exposure to the food he is allergic to. If you suspect you may be having severe allergic symptoms, call 911 immediately.
Common symptoms are dermatologic (rash, swelling), respiratory (coughing, wheezing, throat tightness, change in voice quality), gastrointestinal (abdominal pain, vomiting, diarrhea) or circulatory (hypotension, syncope). The most concerning problem is anaphylaxis, a serious allergic reaction that is rapid in onset and may cause death. Anaphylaxis most often involves at least two body systems -- but any reaction that involves a body system beyond the skin is concerning.
Vandana  R. Sheth
Nutrition & Dietetics
Symptoms of food allergy reactions could vary. According to the Food Allergy & Anaphylaxis Network "reactions may begin with a tingling sensation, itching, or a metallic taste in the mouth. Other symptoms can include hives, a sensation of warmth, wheezing or other difficulty breathing, coughing, swelling of the mouth and throat area, vomiting, diarrhea, cramping, a drop in blood pressure, and loss of consciousness. These symptoms may begin anywhere from several minutes to two hours after eating an offending food, but life-threatening reactions may get worse over a period of several hours. Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death. The symptoms of anaphylaxis can include any of those associated with an allergic reaction to food."

Typical symptoms occurring minutes to an hour or two after a food is eaten.  Typical symptoms include: ones affecting the skin with hives that look like mosquito bites, swelling and itching of the skin often including lip swelling, and skin rashes; gut symptoms such as nausea, vomiting and diarrhea; breathing symptoms such as throat tightness, repetitive cough, wheeze and symptoms could be severe including trouble breathing; and potentially blood circulation can be compromised leading to paleness, blue color, dizziness, confusion or fainting.  In its most severe form, anaphylaxis, severe allergic reactions can be fatal. 

In addition to these immediate reactions, there are a variety of symptoms and illnesses that might signal a food allergy.  These are primarily persistent and chronic symptoms affecting the skin or gut.   Some typical symptoms that may raise suspicion are rashes of atopic dermatitis, blood in infant stool, having poor growth and chronic vomiting, diarrhea or reflux.  It is rare for food to be the sole trigger of asthma or hay fever.  There is no clear evidence that food allergy causes behavioral problems, bed wetting, headaches, joint pains, fevers, infections, fatigue, or acne.  There are many causes and triggers of chronic symptoms that might be attributed to food so it is important to work with your doctor, and often a Board-certified allergist, to determine a cause, whether a food or alternative explanation. 

Michael T. Murray, ND
Naturopathic Medicine

Food allergies are associated with a multitude of symptoms and health conditions:

• Gastrointestinal: Canker sores, celiac disease, chronic diarrhea, duodenal ulcer, gastritis, irritable bowel syndrome, malabsorption, ulcerative colitis

• Genitourinary: Bed-wetting, chronic bladder infections, nephrosisImmune: Chronic infections, frequent ear infections

• Mental/emotional: Anxiety, depression, hyperactivity, inability to concentrate, insomnia irritability, mental confusion, personality change, seizures

• Musculoskeletal: Bursitis, joint pain, low back painRespiratory: Asthma, chronic bronchitis, wheezing

• Skin: Acne, eczema, hives, itching, skin rash

• Miscellaneous: Arrhythmia, edema, fainting, fatigue, headache, hypoglycemia, itchy nose or throat, migraines, sinusitis
The symptoms of an allergic reaction to a food range from tingling tongue and lips to abdominal cramps to difficulty breathing and, in the most serious cases, shock. The reaction site and its severity can vary a lot. When there are two or more organ systems are involved or if there's wheezing, then the reaction is considered severe. The reactions may get worse and worse with subsequent exposures. Just because someone has had only mild reactions to a food doesn't mean that the next reaction won't be serious and potentially fatal.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.