What Are Food Allergies? Symptoms, Causes, Diagnosis, Treatment, and Prevention
Food allergies occur when the body has an immune reaction to proteins in certain foods. The allergic reaction can range from mild to life-threatening, and can cause a variety of symptoms that affect the skin, digestive tract, and respiratory system. Food allergies often begin in childhood, but they can occur at any age.
Symptoms can typically happen within two hours of exposure or ingestion, but they often start within minutes. In rare cases, it can take four to six hours or even longer for symptoms to appear.
The most common symptoms include the following:
“You can even have central nervous system symptoms, including confusion and loss of consciousness,” says Aikaterini Anagnostou, MD, the co-director of the food allergy program at Texas Children’s in Houston and the chair of the American College of Allergy, Asthma & Immunology Food Allergy Committee.
Anaphylaxis can be fatal and must be treated right away with an injection of epinephrine (adrenaline), she says.
A combination of genetics and environmental factors are thought to result in the development of food allergies, says Dr. Anagnostou.
There are many theories on why that may be happening. The leading one is labeled the “hygiene hypothesis.” The basic idea is that living in an extremely clean household may affect the balance of their immune system, explains Anagnostou.
“The immune system is no longer exposed to as many pathogens as it used to be, so perhaps the immune system is trying to find other sorts of things to react to that are not pathogens. It's overreacting to things that it shouldn't, like foods,” she says. This hasn’t been proven, but it’s a hypothesis that could explain why food allergies are more common now.
Once you suspect that you may have a food allergy, you should visit your primary care physician, recommends Sindher. “Food allergies are easy to misdiagnose, since it shares many symptoms with similar diseases and conditions such as food sensitivity, food intolerance, and food poisoning.” If a food allergy is strongly suspected, then an allergist can perform the necessary tests to confirm which foods are causing the reaction and offer guidance on what do next.
The gold standard for diagnosing food allergy is the oral food challenge. “In an oral food challenge, the individual eats increasing amounts of the allergen in a controlled clinical setting to assess for the development of an allergic reaction,” explains Sindher.
But usually other tests are used to screen whether the oral food challenge is necessary, such as skin prick testing and allergen-specific immunoglobulin E testing, she says.
If you aren’t having any symptoms or reactions to a food, you aren’t allergic to it, notes Anagnostou. “Sometimes people get a blood test, and they have higher levels of immunoglobulin E, but that’s not enough for a diagnosis, and it doesn’t mean they are allergic to that food. You need to have a history of reaction together with positive testing,” she explains.
Doing random food allergy tests without any symptoms can lead to getting incorrectly labeled as allergic to certain food or foods, she cautions.
Food Elimination Diet You should try a food elimination diet only under the advice and supervision of an allergist. The first step is to stop eating all the suspected foods for about two weeks, then slowly add them back to your diet one at a time.
If you have symptoms after adding back a certain food, it may confirm an allergy.
What’s the difference between a food allergy, food intolerance, or food sensitivity? They are often mistaken for the others and are sometimes difficult to separate, Sindher notes. A food allergy is due to the actions of the food allergen-specific IgE antibodies that recognize the protein in the food and result in an immune reaction, but food sensitivities or food intolerance lack those antibodies, she explains.
Food intolerances can cause diarrhea, gas, bloating, heartburn, nausea, upset stomach, and stomach pain, but the symptoms aren’t life-threatening.
Symptoms of a food sensitivity can be similar to a mild allergic reaction and include fatigue, flushed skin, itching, joint or muscle pain, headache or migraine, a runny or stuffy nose, and sneezing.
The reaction may be delayed and could evolve over several days.
Celiac disease is not in any of the above categories. It’s an autoimmune disorder triggered by small amounts of gluten.
There is currently no cure for food allergies. Treatment strategies and medications for food allergies include the following:
Avoidance of Foods That Trigger an Allergic Response This requires carefully checking the ingredients in packaged foods and being aware that the food you should avoid may have more than one name. Though food avoidance is necessary, this is often difficult to truly achieve as allergens are often present in common foods, including foods that you would not normally consider checking, says Sindher.
Epinephrine (Adrenaline) Epinephrine is commonly used for anaphylaxis, when exposure to a food triggers a flood of chemicals that can send the body into shock. This reaction can happen in seconds or minutes, and can be fatal.
Recent advancements like omalizumab (Xolair) offer promising avenues for severe allergy management. For a long time, food avoidance and epinephrine were the only options, but now there are other ways to protect individuals from the risk of allergic reactions due to accidental ingestion, says Sindher.
Omalizumab provides you with a safety net to reduce the risk or intensity of an allergic reaction, but people still need to avoid eating the allergen, she cautions.
Oral Immunotherapy “If your long-term goal is to be able to eat small amounts of the allergen, oral immunotherapy can give you a greater degree of protection,” says Sindher. Oral immunotherapy is the controlled ingestion of small amounts of allergen (low enough to avoid triggering an allergic reaction) over a long period of time, she explains.
“The amount of the allergen is slowly increased under the supervision of a medical practitioner until a target maintenance dose is reached and maintained for a long period of time,” explains Sindher.
The therapy carries a continued risk of anaphylaxis. In clinical trials, about 9 percent of Palforzia-treated participants reported a reaction during the buildup and maintenance phase of the trial. As with anyone with food allergies, people taking the therapy must have injectable epinephrine available for immediate use at all times.
This isn’t a cure, but it can reduce the risk and severity of allergic reactions when exposed to the allergen. Also, you have to keep taking it if you want to continue to benefit from its protection. Missing it for too long can result in loss of protection,” she says.
Other medications under investigation include allergy skin patches, allergy drops, and toothpaste for peanut, milk, and egg allergies, notes Sindher.
There isn’t any known way to prevent a food allergy from happening once a person has it, but there are ways to reduce the risk of ever developing food allergies. “For example, we know that early food introduction, giving allergenic foods to infants and babies in the appropriate form, can actually reduce the risk of developing food allergies,” says Anagnostou.
That advice has changed over the years — it used to be to wait before you introduced foods like peanuts or eggs. “Now we know that it may reduce the risk of being allergic to those foods,” she says.
Complications of food allergies extend beyond immediate allergic reactions and can include a psychological and social burden, says Sindher.
Anaphylaxis This reaction can include hives and flushing, swelling of different parts of the body, and respiratory symptoms such as wheezing and shortness of breath. Reduced blood pressure, fainting, incontinence, vomiting, and abdominal pain can be part of anaphylaxis, too.
The reaction also includes acute and rapid onset — within minutes to hours — of low blood pressure or airway involvement that makes breathing difficult.
Social Burden Having a food allergy has a much broader impact on food allergic individuals than many people realize, notes Sindher. “Eating out means that you don’t have full knowledge of all the ingredients in your food, which is very stressful for food allergic individuals. This stress often leads to missing social activities, avoiding airline travel, and changing family traditions,” she says.
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