Food allergies occur when the body’s immune system reacts to certain proteins in food. There are several foods that seem to cause more allergic reactions than others, but people can become allergic to almost any kind of food.
In this article, I’ll explain what food allergies are, symptoms of an allergic reaction, and the eight most common food allergies. I’ll also address the different types of food allergies, as well as how food allergies are diagnosed and treated.
What Are Food Allergies?
Food allergies are abnormal immune system responses to proteins found in foods. While the immune system is designed to protect the body against infections or germs, sometimes it can mistakenly become sensitized to other things such as food proteins.
It then produces antibodies and mounts an attack any time it is exposed to that ingredient. Allergic reactions can occur from exposure to small amounts of a trigger food, or when a food has been prepared in the same area as food someone may be allergic to.
So people who have allergies need to read packaged food labels and ask questions when they eat in restaurants or are served new or unfamiliar foods.
It is also possible to have negative reactions to foods that are not caused by allergies, though it can be tough to tell the difference. True food allergies are caused by an immunoglobulin E (IgE) antibody response from the immune system.
Potential Symptoms of a Food Allergy
Food allergy reactions can happen within minutes after being exposed or may take a few hours or days to appear.
Symptoms can include:
- Itchy rash
- Swelling of the face, mouth, or tongue
- Problems breathing
- Low blood pressure
These side effects can happen in a more severe way known as anaphylaxis. When this happens, many symptoms may be the same, but they come on faster and more severely, typically with more pronounced breathing problems.
Anaphylaxis is a medical emergency. If not properly and immediately responded to, anaphylaxis and severe food allergy reactions can be fatal. Medical providers prescribe people who have anaphylactic allergies epinephrine injection pens to use if they show signs of anaphylaxis.
If you have a severe food allergy reaction, seek emergency medical care, even if you control the reaction with epinephrine.
Common Food Allergies
Most food allergies are caused by eight common foods.
While this allergy affects 2-7.5% of infants and young children, 90% of cow’s milk allergies are outgrown by adulthood. Adults may struggle with lactose intolerance, but cow’s milk allergies in adults are rare.
Children who have allergic reactions to the proteins in cow’s milk typically show signs within minutes. Anaphylaxis and other serious allergic reactions, like swelling and breathing problems, may be common.
Cow’s milk allergies require total avoidance of foods that contain it, including:
- Milk and milk powder
- Dairy-based formula
- Cream cheese
- Sour cream
- Ice cream
- Whey protein
Cow’s milk allergies can happen in infants who are fed formula or breast milk. If a baby who is breastfed is diagnosed with cow’s milk allergy, the breastfeeding parent must also remove all foods that contain cow’s milk from their own diet. For formula-fed infants, non-dairy and other specialized formulas are available.
Allergies to chicken eggs are the second most common food allergy in kids. More than 60% of kids who are allergic to egg white or egg yolk protein are able to eat foods containing baked eggs because the heat reshapes the proteins and decreases the immune system’s response.
Some children may be allergic to only the whites or the yolks, not both, but egg white allergies are more common.
Of children who have egg allergies:
- More than 60% are allergic to other foods
- Almost 30% have a peanut allergy
- Nearly 70% outgrow the allergy by the time they are teenagers
- Almost half also have asthma
Although less common, adults who were never allergic to eggs as children can develop an allergy to them.
Tree nut allergies affect 1-3% of the worldwide population. A person can be allergic to a specific tree nut or have reactions to most or all of them. The most common tree nut allergies involve hazelnuts, walnuts, cashews, almonds, and Brazil nuts.
It is also possible to be allergic to macadamia nuts, pistachios, pine nuts, and any other type of tree nut. People with tree nut allergies must also avoid any products made with ingredients derived from tree nuts, including nut butters, nut oils, and milk alternatives like almond milk.
Medical providers typically advise patients who have serious tree nut allergies to avoid all types of tree nuts to reduce the risk of an allergic reaction due to cross-contamination or the mixing of nuts during packing. Unlike other types of allergens, tree nut allergies are usually lifelong.
Although less common than some other allergies, nut allergies cause half of all deaths related to anaphylactic reactions to food. Like other types of anaphylactic allergies, people who have tree nut allergies are prescribed epinephrine auto-injectors and should carry them at all times.
Peanut allergies are common and can be severe. Along with tree nut allergies, they cause half of all anaphylactic-related fatalities. Peanuts are not grouped with tree nuts because peanuts are legumes.
Someone can be allergic to tree nuts but not peanuts, and vice versa. Peanut allergies can develop in infants and young children before they eat peanuts by exposure through the skin. Even without a history of peanut allergy as a child, adults can develop severe peanut allergies.
Studies have found that more than 17% of adults with peanut allergies developed them as adults. Peanut allergies that occur in childhood may be permanent, although between 15-22% of children may outgrow peanut allergies as teenagers.
Shellfish allergies include being sensitized to crustacean and mollusk types of seafood such as:
These types of allergies are typically lifelong. Shellfish allergies can lead to anaphylactic responses.
People who are seriously allergic to shellfish can get sick from being in or around shellfish when it’s being cooked, or by breathing in the vapors that come off of shellfish. To prevent reactions, those with particularly severe shellfish allergies may need to entirely avoid homes and restaurants that serve shellfish.
A wheat allergy is different from sensitivity to gluten and Celiac disease (where consuming gluten leads to damage to the intestinal lining). Wheat allergy is an immune-driven response to wheat protein, which contains hundreds of different types of protein.
People who have Celiac disease must avoid gluten from all sources, including non-wheat sources. Since they are only allergic to wheat, people who have wheat allergies do not have to avoid gluten from non-wheat sources.
Wheat allergy is more common in children and may be outgrown by the age of 10. However, there is the potential for severe reactions, anaphylaxis, and death if not properly treated.
Soy allergies are most commonly seen in younger children. They are caused by soybeans and any products that contain soy.
As many as 70% of children who develop soy allergies may grow out of them. Soy is rarely a cause of anaphylaxis and most commonly leads to symptoms such as runny nose, breathing problems, itchy mouth, and vomiting.
Fish allergies are different from shellfish allergies, although people may have both. Fish allergies can develop in childhood or adulthood and affect around 7% of adults.
Fish allergies can have serious anaphylactic reactions and, if not treated promptly, can be fatal. People who have fish allergies are usually prescribed epinephrine auto-injectors, which they should carry at all times.
Other food allergies
While the eight food allergens above are the most common, people can develop allergies to almost any protein in any type of food.
Other food allergies that may occur include:
- Sesame seeds
- Red meat
- Passion fruit
- Mustard seeds
Types of Food Allergies
Food allergies are divided by the type of response they trigger in the body.
Immunoglobulin E (IgE)-mediated
IgE-mediated allergies are the most serious type of food allergy and can be associated with breathing problems, hives, and anaphylaxis.
They happen when the immune system produces an antibody to the specific food protein, resulting in the sudden flareup of symptoms if the food is ingested or there is contact. Symptoms may be mild to severe and usually show up within a few hours.
In a non-IgE-mediated allergy, the immune system does not make IgE antibodies. Instead, other parts of the immune system produce a response to the food protein.
Symptoms are less likely to be severe or cause an anaphylactic reaction, but can involve nausea, vomiting, digestive upset, and itchy or red skin. Non-IgE allergic reactions can happen within hours or might not appear for up to three days after the allergen exposure.
Non-IgE-allergies are different from food sensitivities, food intolerances, and other digestive symptoms that may occur in non-allergic medical conditions like Celiac disease.
Diagnosing a Food Allergy
Food allergies can sometimes be difficult to diagnose, especially if they do not produce typical symptoms or the symptoms take several days to appear.
If you think you or your child have a food allergy, see a healthcare provider.
They may order one or more types of tests to diagnose a food allergy:
- Skin prick testing uses a tiny needle to insert a small part of the food protein into the surface of the skin. The provider then monitors to see if a reaction occurs. This is the most accurate and common way to diagnose food allergy.
- Blood tests check for IgE proteins to see if the immune system reacts to certain foods. It is possible to have false positives and false negatives with this type of test, although it can help confirm skin prick testing results that are not definitive.
- Oral food challenges may be done if an allergy is suspected but not confirmed by other tests. This can also test to see if someone has outgrown a food allergy. Oral challenges can only be done safely by medical professionals in supervised healthcare settings fully equipped to handle an allergic response if one happens.
Treating a Food Allergy
Food allergies cannot be cured, although people may outgrow them over time. The proper treatment for food allergy is total avoidance of the food and any potential foods that contain trace amounts or contaminants.
Medications for food allergies
If you are diagnosed with a food allergy, your doctor may prescribe one or more medications:
- Epinephrine auto-injectors are for people who have severe or anaphylactic allergic reactions to foods. These should be with the person at all times. Family members and friends should also be trained how to use these in case of emergency.
- Antihistamines are for less severe allergic reactions or to be used in conjunction with epinephrine auto-injectors. Medications that are related to antihistamines, including H2 blockers such as Famotidine, can also be taken.
- Corticosteroids can be taken to decrease swelling that occurs from allergic reactions, and may be prescribed individually or with other allergy medications.
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