Table of ContentsView AllTable of ContentsBiological CausesEnvironmental CausesGenetic FactorsRisk FactorsFrequently Asked QuestionsNext in Food Allergies GuideHow Food Allergy Is Treated
Table of ContentsView All
View All
Table of Contents
Biological Causes
Environmental Causes
Genetic Factors
Risk Factors
Frequently Asked Questions
Next in Food Allergies Guide
To add further confusion, there are times when a food allergy may be considered a “true allergy,” while others may be regarded as cross-reactive (meaning that the body reacts to what itthinksis the true allergy).
Food allergies should not be confused with allergy-like reactions to food (known asfood intoleranceor non-allergic food hypersensitivity). Examples includelactose intoleranceandsulfite allergy.
At its heart, an allergy is a “case of mistaken identities” in which the immune system regards a harmless substance as harmful.
Laura Porter / Verywell
With an allergy, the immune system will overreact to an otherwise harmless antigen, referred to as anallergen. In launching a defense, the immune system will release a type of antibody known asimmunoglobulin E(IgE). Among other things, IgE will spur the release of inflammatory chemicals, such ashistamine, which cause the skin, lung, nasal, and throat symptoms we recognize as an allergy.
Each type of IgE the body produces has specific “radar” for each type of allergen. That is why some people may only be allergic to wheat, while others may be susceptible to multiple allergens.
In the United States, allergies to milk, eggs, wheat, fish, soy and peanuts are most common in children. In adults, fish, shellfish, peanuts, oleaginous fruits (nuts, seeds), and certain fruits (especially cherries, peaches, plums, apricots) are the predominant culprits.
Generally speaking, it is protein that acts as the primary food allergen. Such is the case with the proteins found in eggs, which can cause allergy when eaten, incorporated into other foods, or used to makevaccines.
Recognizing Soy Allergy Symptoms
The food traditions of a country will influence which foods the population will most likely be allergic to.
For example, in Northern Europe, cod is a staple of the regional diet and the most common cause of food allergy.In Italy, where vegetables comprise a higher proportion of the national diet, allergies to raw vegetables, tomatoes, and corn are common.The same can be seen in East Asia where rice is a staple food and the primary source of food allergies.
Common Food Triggers
Despite these regional variations, the World Health Organization (WHO) compiled a list consisting of eight foods that cause the most allergies globally, namely milk, eggs, peanuts, tree nuts, fish, shellfish, soy, and wheat.
In the United States, the U.S. Food Drug and Administration (FDA) has mandated thatmilk,eggs,peanuts,tree nuts,fish,crustacean shellfish,soybean, sesame, and wheat—which account for 90% of food allergies—be prominently listed on the product labels of any food containing them.Sesame was added to this list in 2023.
Of these, allergies to eggs, milk, wheat, peanuts, and soybean are more common in infants and young children,while older children and adults are more likely to be allergic to peanuts, tree nuts, and shellfish.
Sensitization
The reason why people are allergic to these or any other foods is not entirely clear. During the course of encountering a certain food, the immune system will decide whether to tolerate it or be sensitive to it. The latter process, calledsensitization, is the mechanism that scientists still don’t fully understand.
There, it encounters immune cells, called regulatory T-cells (Tregs), that regulate the immune response. At this stage, the Tregs will either tolerate the protein or activate the immune system and launch an attack.
With regards to food allergies, sensitization typically occurs in the digestive tract. While some researchers contend that food sensitization can occur via the skin, presumably as an extension ofcontact dermatitis, there is little actual evidence of this.
How to Recognize and Treat an Allergic Reaction in Babies and Infants
Atopy
Scientists don’t believe Treg activation is simply a fluke. It may be that the Tregs are defective, but it also possible that a person has a predisposition to allergies, a condition referred to as atopy or atopic syndrome.
Atopy is believed to occur when a person is exposed to numerous allergens via the skin, respiratory tract, and digestive tract.These may include things like food, pollen, chemicals, pet dander, and dust mites. In some people, these exposures will leave the immune system in a heightened state of alert, placing them at risk of not one but multiple allergies.
People withallergic rhinitis,allergic conjunctivitis,eczema, and asthma are far more likely than food allergies than those who don’t, according to a2018 studyinCurrent Treatment Option in Allergy.
Environmental Factors
But atopy doesn’t entirely explain food allergies given that infants with little environmental exposure may also experience reactions. Within this population, it is the absence of an immune defense that characterizes the risk.
Scientists contend that children exposed to common food allergens will react because their immune systems don’t yet recognize them. As their immune systems mature and the children gain exposure to a broader range of substances, their body will be better able to differentiate between harmless and harmful substances.But it is not always the case.
As contradictory as this may seem, adult-onset food allergies are even more perplexing. Although little is known about the cause of the sudden onset, most scientists believe that sudden or severe changes in the environment may play a key role.Among the theories:
Others still insist that cross-reactivity—in which the presence of one allergy triggers others—is the primary cause of food allergies in adults.
Cross-Reactivity
Cross-reactivity describes an allergic reaction in which the body responds to one protein that is similar in structure to another protein. As such, the immune system will see both substances as the same. In the case of food allergies, examples of cross-reactivity include:
There are other cases when a food allergy is secondary to atrue allergy. One such example islatex-food syndromein which an allergy to latex can cause an allergic response to food like avocado, banana, kiwi, or chestnut (each of which contains traces of the latex protein).
Alatex allergyis considered a true allergy because having it increases your risk of a food allergy. By contrast, an avocado, banana, kiwi, or chestnut allergy is secondary because it does not increase your risk of a latex allergy.
A similar condition occurs withoral allergy syndrome(OAS) in which the presence of a true allergy can cause allergy symptoms when cross-reactive foods are eaten. With OAS, the true allergy usually involves tree or grass pollens but may also include aerosolizedmold spores. Examples of OAS Include:
The 9 Most Common Food Allergies
Similar familial links have been seen with seafood and other common food allergies.
To date, only a handful of suspect gene mutations has been identified.Most belong to a group of genes known as the human leukocyte antigen (HLA) complex. Among their many functions, HLA genes are responsible for encoding antigens on the surface of cells. Errors in the coding may explain why the immune system will suddenly see harmless cells as dangerous.
Other mutations involve the Filaggrin (FLG) gene which encodes proteins in skin cells, the Catenin Alpha 3 (CTNNA3) gene which encodes proteins in muscle cells, and the RNA Binding Fox-1 Homolog 1 (RBFOX1) gene which encodes proteins in nerve cells.
While this may suggest thatgenetic testingcan be used to establish your risk of allergies, mutations on their own do not cause allergies.
From an epidemiological standpoint, there are six key factors associated with the development of a food allergy:
While changes in geography may remove you from the allergens that trigger your allergies, exposure to new substances (including those you eat, breathe, or touch) can potentially trigger new ones.
Frequently Asked QuestionsFood allergies are caused when the immune system responds to certain food proteins as if they were a threat. When this happens, the immune system will release chemicals, including histamine, that cause blood vessels and tissues to swell, triggeringsymptomslike runny nose, rash, watery eyes, and sneezing.There are actually two categories of food allergy:IgE-mediated food allergiesare those involving anantibodycalled immunoglobulin E (IgE) that usually triggers allergy symptoms within minutes.Non-IgE-mediated food allergiesinvolve other parts of the immune system and tend to trigger a delayed reaction, causing gastrointestinal symptoms like nausea, vomiting, or diarrhea.The eight most common food allergies are:EggsFishMilkPeanutsShellfishSoyTree nutsWheatEggs, milk, and peanuts are the most common causes of food allergies in children. Although some children “outgrow” their allergies, others may have them for a lifetime.Shellfish is the most common food allergy in adults, along with tree nuts, peanuts, and fish. The majority of adults with food allergies had food allergies as children.Not always. There is a condition called oral allergy syndrome (OAS) in which proteins of certain foods are similar to allergenic proteins of certain pollens and can trigger generally milder symptoms like an itchy mouth or the swelling of the mouth or lips. For example, if you’re allergic to birch pollen, raw apples might trigger OAS symptoms.Some can be, and there is no real way to tell who might develop a severe reaction. This includes a potentially life-threatening, whole-body allergy calledanaphylaxis. Anaphylaxis is a medical emergency that can lead toshock, coma, suffocation, heart or respiratory failure, and death if left untreated.In children, peanuts, tree nuts, fish, shellfish, milk, and eggs account for the greatest number of anaphylactic reactions. Shellfish is the most common trigger in adults.
Food allergies are caused when the immune system responds to certain food proteins as if they were a threat. When this happens, the immune system will release chemicals, including histamine, that cause blood vessels and tissues to swell, triggeringsymptomslike runny nose, rash, watery eyes, and sneezing.
There are actually two categories of food allergy:IgE-mediated food allergiesare those involving anantibodycalled immunoglobulin E (IgE) that usually triggers allergy symptoms within minutes.Non-IgE-mediated food allergiesinvolve other parts of the immune system and tend to trigger a delayed reaction, causing gastrointestinal symptoms like nausea, vomiting, or diarrhea.
There are actually two categories of food allergy:
The eight most common food allergies are:EggsFishMilkPeanutsShellfishSoyTree nutsWheat
The eight most common food allergies are:
Eggs, milk, and peanuts are the most common causes of food allergies in children. Although some children “outgrow” their allergies, others may have them for a lifetime.
Shellfish is the most common food allergy in adults, along with tree nuts, peanuts, and fish. The majority of adults with food allergies had food allergies as children.
Not always. There is a condition called oral allergy syndrome (OAS) in which proteins of certain foods are similar to allergenic proteins of certain pollens and can trigger generally milder symptoms like an itchy mouth or the swelling of the mouth or lips. For example, if you’re allergic to birch pollen, raw apples might trigger OAS symptoms.
Some can be, and there is no real way to tell who might develop a severe reaction. This includes a potentially life-threatening, whole-body allergy calledanaphylaxis. Anaphylaxis is a medical emergency that can lead toshock, coma, suffocation, heart or respiratory failure, and death if left untreated.
In children, peanuts, tree nuts, fish, shellfish, milk, and eggs account for the greatest number of anaphylactic reactions. Shellfish is the most common trigger in adults.
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