Food Allergens

 

Egg white | Cow's milk  | FishWheat | Peanut | Soy | Hazelnut | Shrimp

 

 f1 Egg white

Allergen description

Gallus spp.

Egg is a major cause of adverse reactions in infants and hidden exposure is common.

Hens’ eggs are composed of about 60% egg white and 30% egg yolk. Egg white contains approximately 88% water and 10% protein.

The major allergens of egg white are ovomucoid, ovalbumin, ovotransferrin (also called conalbumin), and lysozyme.

Allergen exposure

Expected exposure

  • Cooked or raw eggs
  • Bread and pastry
  • Numerous dishes like pancakes, sauces, etc.

Unexpected exposure

  • Candy
  • Beverages
  • Meat products like sausages, pâtés, etc.

A great variety of foods may contain egg or traces of egg and patients allergic to egg need to be aware of egg as a frequent “hidden” allergen.

Cross-reactivity

  • Eggs from related animals
  • Presence of shared allergens in egg-white, egg-yolk, serum and meat from hen and chicken has been demonstrated.

Clinical experience

IgE-mediated reactions

Egg-specific IgE antibodies are usually the first antibodies to appear in children developing atopic disease.

Allergy to egg is generally considered to be one of the most common causes of food allergy in infants and young children. When studying egg-allergic children, IgE antibodies were found in more than 65% of children with eczema and respiratory tract symptoms.

Egg-white specific IgE antibodies may predict the development of atopic respiratory allergy. In a follow-up study of infants where the authors had concluded that eggwhite sensitivity was a better indicator of atopy than total serum IgE, the infants presenting with egg-white allergy were more likely to have developed inhalant allergy by 7 years of age. Other studies show similar results.

Egg white is often responsible for early development of urticaria and eczema during infancy.

Remaining egg intolerance in older children and adults may be linked to exposure to cage birds and chicken meat.

Certain vaccines grown on chicken embryos have been reported to cause severe allergic reactions in patients when injected. Further development of vaccines seems to have decreased or even eliminated the risk for egg-allergic children.

 

 

  f2 Cow's milk

Allergen description

Bos spp.

Cow’s milk is a major cause of adverse reactions in infants and hidden exposure is common.

There are many allergenic proteins in milk and caseins, alpha-lactalbumin and beta-lactoglobulin are considered as some of the major allergens. Caseins are heat stable allergens.

Allergen exposure

Expected exposure

  • Milk, cheese and other dairy products
  • Bread and pastry
  • Numerous dishes like pancakes, soups etc.

Unexpected exposure

  • Candy
  • Toppings
  • Processed meat like ham, sausages, pâtés, etc.
  • Hydrolyzed milk formulas

Milk and milk derivatives are used in a wide variety of confectionery products. Contamination during processing or addition of sodium caseinate has also been reported.

Cross-reactivity

  • Milk from related animals
  • Presence of shared allergens in milk, meat, and dander from cow has been demonstrated.

Clinical experience

IgE-mediated reactions

Cow’s milk is a major cause of adverse reactions in infants with prevalence 0.5–7.5%. Some patients retain a lifelong allergy. Cow’s milk-induced asthma is often observed in infants with food hypersensitivity as well as rhinoconjunctivitis and possibly also serous otitis media. Cow’s milk allergy in infants has a much better prognosis for outgrowth than in older children or adults.

IgE antibodies to milk may develop before the onset of clinical allergy, indicating that in vitro measurements can be good predictive tools. Correlation of milk-specific IgE antibody levels with the development of tolerance to milk has been reported.

The symptoms in infants are usually dermatological and gastrointestinal (GI), with eczema often appearing early. In children retaining milk allergy, cutaneous symptoms decrease while respiratory and GI symptoms increase with age. Infants with early sensitization to cow’s milk proteins have an increased risk for later development of other food allergies and sensitization to inhalant allergens.

Other reactions

  • Lactase deficiency (lactose intolerance)
  • Immune reactions without IgE antibody involvement

In adults lactase deficiency is a common cause of milk hypersensitivity.

 

 

  f3 Fish

Allergen description

Gadus morhua

Family

Gadidae

The Atlantic cod is one of the world’s most important food fish. It is sold fresh, frozen, smoked, salted and canned.

Patients allergic to fish often have dramatic symptoms, such as asthma or anaphylactic reactions. Some patients allergic to one fish may tolerate other fish species.

Allergen exposure

Expected exposure

  • Meat from cod

Unexpected exposure

  • Undeclared ingredient in industrially prepared food,
  • such as cured meat products
  • Contamination of cooking oil, utensils and containers
  • Inhalation of steam or dried fragments

Cross-reactivity

Species within groups of fish, like Gadiformes (e.g. codfish and hake) and Scombroid fishes (e.g. mackerel and tuna) seem to share allergenic components. The overlap of allergen specificity between the groups seems to be moderate.

However the major cod allergen (parvalbumin) seems to be a good representative for many fish species.

Clinical experience

IgE-mediated reactions

Allergic reactions to fish are a common cause of food allergy. Prevalence figures vary from approx. 10% to approx. 40% in atopic populations. In Norway fish allergy was found in 1/1000 of the general population. While many children often outgrow allergy to cow’s milk and egg white, those allergic to fish may continue to be hypersensitive to fish later in life.

Reactions to fish allergens are often severe. Systemic reactions after eating fish, but also after inhaling steam or aerosol in connection with cooking or handling fish or after skin contact are reported in several studies.

Extremely sensitive patients have suffered anaphylactic shock after eating foods cooked in re-used cooking-oil, or when utensils and containers have been used earlier for cooking fish.

Many patients avoid all species of fish and others may tolerate a few, thus indicating specific allergens.

Because patients react to both cooked and raw fish, it is assumed that the allergens are heat-resistant. However, more recent studies indicate that patients may react differently to processed food and that allergic reactions may also be species-specific.

 

 

  f4 Wheat

Allergen description

Wheat is one of the major cereal grains belonging to the grass family and a staple food item in most diets worldwide.

There are many different types of wheat, but the hexaploid Triticum aestivum is by far the most important of the Western species.

The major proteins in wheat (albumins, globulins and glutens) vary in proportion according to the type of wheat. This variability is one reason why reactions to different wheat products are not consistent.

Allergen exposure

Expected exposure

Softer wheat with lower protein content is used for biscuits, cakes and pastry, harder wheat with higher protein content for bread, semolina, cous-cous, macaroni and pasta. Durum wheat is a source of Italian pasta, Indian chappatis and Chinese noodles. Wheat is also a source of alcoholic beverages such as beer.

Unexpected exposure

Wheat is used in livestock feed. Wheat starch is used for pastes and for sizing textiles.

Cross-reactivity

An extensive cross-reactivity among different individual species of wheat as well as some cross-reactivity to grass pollens could be expected.

Clinical experience

IgE-mediated reactions

Wheat is among the six most important food items accounting for IgE mediated allergic reactions in children.

IgE mediated allergic reactions to ingested wheat protein include gastrointestinal, respiratory and cutaneous symptoms. Reactions typically occur within an hour of wheat ingestion. Affected individuals are usually sensitized during infancy and the clinical reactivity typically resolves before adulthood.

Wheat exposure may result in different life-threatening anaphylactic reactions. Wheat dependent exercise-induced anaphylaxis (WDEIA) is a severe IgE-mediated allergic reaction provoked by the combination of wheat or wheat flour ingestion and intense physical exercise during the next few hours.

Sensitization by inhalation can cause baker’s asthma, a frequent allergy in the baking industry. Occupational exposure to wheat or wheat dust may also result in other allergic conditions affecting animal, bakery, food industry and mill workers.

Other reactions

Wheat allergy and celiac disease are two distinct conditions. Celiac disease is a permanent non-IgE mediated reaction caused by intolerance to gluten.

 

 

  f13 Peanut

Allergen description

Arachis hypogaea

Family

Fabaceae

Peanut is not a nut, but a seed of an annual legume. It grows close to the ground and produces its fruit below the soil surface, in contrast to tree nuts like walnuts and almonds. Peanut is a member of the Fabaceae or legume family, whereas tree nuts are not.

Peanuts were first cultivated in South America. Portuguese explorers then transplanted peanut plants to Africa, and from there peanuts were spread to the rest of the world by explorers.

Allergen exposure

Expected exposure

Peanuts are consumed mainly as peanut butter and as snacks (roasted, salted, plain or dry roasted), but also in other foods.

Unexpected exposure

Peanuts occur in candy and in baked goods. Peanuts also yield widely used oils. Arachis oil is peanut oil. Peanut flour is an important ingredient in a variety of processed foods. Another unexpected source of peanuts is foods served at restaurants often using peanut as an ingredient, such as the Asian and African cuisines.

Cross-reactivity

Peanut and tree nut allergic reactions coexist in 25-50% of peanut allergic patients, and allergic reactions to tree nuts such as walnuts, cashews, pecans and pistachios can develop even though tree nuts belong to a different botanical family. Reactions frequently occur on first exposure and may be life-threatening. It is unclear whether this is due to genuine cross-reactivity or to the coexistence of separate allergies in widely atopic individuals.

Although peanut shares homologous proteins with botanically related beans and legumes, the majority of patients do not show clinical reactions to other legumes. Although one would expect that peanut-allergic individuals would have a high risk of cross- or co-reactivity to soybean (a family member), blinded food challenges have shown a low rate of these reactions. However, it is still not clear whether peanut allergic patients also should avoid soybeans or not.

Clinical experience

IgE-mediated reactions

Peanuts are a significant cause of serious food allergy in both adults and children. Peanut allergy usually begins in childhood and unlike other food allergies often persists throughout the affected individual’s lifetime. Only approx. 20% of young children will develop tolerance.

Allergic reactions to peanut can be mild to moderate, but compared to reactions to other food allergens they might be more likely to be severe or even fatal. Atopic dermatitis, angioedema, asthma, diarrhea, nausea and vomiting, and anaphylaxis have been reported. Urticaria may be a prominent symptom. Although not reported frequently, asthma may be a significant feature in peanut allergy. As severe peanut allergy in asthmatic infants carries a risk of anaphylaxis, it is useful to look for peanut allergy in all infants with severe asthma. Peanut dust can also act as an inhalant allergen.

 

 

  f14 Soy

Allergen description

Glycine max (Soja hispida)

Family

Fabaceae

Soybeans are dried ripe seeds and a high-protein legume grown as food for both humans and animals. It is an important source of protein to many vegetarians and vegans. The word soy is derived from the Japanese word shoyu (soy sauce).

Allergen exposure

Expected exposure

The bean can be fresh, processed into soybean flour or pressed for oil. Soybean oil is put to many uses. For example it is included in salad oil and margarine. Some soy allergic patients may safely eat soybean oil (not cold pressed, expeller pressed or extruded oil) and soy lecithin, while extremely soy allergic patients may react to traces of soy protein in soybean oil and soy lecithin.

Soybeans and products made from the bean (miso, tofu, natto, douchi, etc.) are significant parts of the diet in Asia. Soy sauce, or shoyu, is a fermented product of soybean and wheat.

Soybean oil is also used in industrial components and in linoleum and glue in the plywood industry, where it is considered an occupational allergen.

Unexpected exposure

Soy proteins are frequently found in meat products, bread and other industrially produced food products. The list of food products presenting potential risk is expanding. Some examples are sausage products, pizza and candy containing soy lecithin.

Cross-reactivity

Already in studies of soybean allergenicity, soybean was found to contain several antigenic components with considerable cross-reactivity with other legume family members. While the clinical relevance of eliminating legumes as a food group from the diet of allergic patients is disputed, several reports confirm cross-reactivity e.g. to peas, lentils, peanuts, kidney, lima and navy beans.

Clinical experience

IgE-mediated reactions

Soybean is considered a “classical food allergen” and is one of the foods to which children often have allergic reactions. Allergic reactions to soybean are dominated by stomach and skin problems, but also include respiratory symptom as well as severe allergic reactions. With its expanding use as a constituent in many different foods, soybean may be an underestimated cause of severe allergic reactions.

There is an ongoing debate on the use of soy formula as a safe substitute for infants with cow’s milk allergy.

In some countries it is recommended as a safe alternative when screening results indicate no existing soy allergy. However, there are also studies reporting on the risk of developing allergy to soy when using soy formula, and about one-fourth of cow’s milk-sensitive patients have been reported to become allergic to soy protein. Therefore, some countries recommend that breast-feeding or less allergenic formulas should be preferred.

Patients experiencing IgE-mediated symptoms after ingesting peas, beans, lentils, peanuts or soybeans have been reported.

Soybean dust can also act as an inhalant allergen. Epidemic asthma in areas around harbors, where soybeans were unloaded from ships, has been reported from several places around the world. A large number of fatal cases probably involving anaphylaxis were recorded. Occupational asthma in bakers and workers in food processing plants may be caused by soy flour.

 

 

  f17 Hazelnut

Allergen description

Corylus avellana

Family

Corylaceae (Betulaceae)

The terms “filbert” and “hazelnut” are often used inter-changeably for nuts from all plants in the genus Corylus, such as C. silvestris, C. maxima and C. colurna.

These wild nuts grow in clusters on the hazel tree in temperate zones around the world. Hazel is an aggressive spreader and is particularly common in Europe.

Italy, Spain, France and Turkey lead in hazelnut production. The nuts generally fall in autumn and are harvested from the ground and then shelled and dried.

Allergen exposure

Expected exposure

The nuts are used chopped, ground, roasted, blanched, sliced and as flour and paste in all manner of sweets. They are also eaten whole as a snack. Hazelnuts also add flavor and texture to savory items such as salads and main dishes.

Unexpected exposure

Hazelnut is widely used and can be a “hidden” allergen. Nougat, an ingredient in secondary products such as confections, is for example a hazelnut product.

Cross-reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected. Cross-reactivity between hazelnut and hazel tree pollen may occur. There is also a relationship between birch pollinosis and sensitization to hazelnut, apple, kiwi, carrot, potato and other vegetables. In birch pollen-hypersensitive patients with oral allergy syndrome it is very common with apple and/or hazelnut allergy.

An important cross-reactivity between the pollen of Platanus acerifolia (London plane tree), hazelnut and banana has been reported. Partial cross-reactivity has been reported to occur between hazelnut and macadamia nuts.

Clinical experience

IgE-mediated reactions

Hazelnuts are a common cause of food allergy. Allergic sensitization may occur early on in life. Allergic reactions to hazelnuts range from oral allergy syndrome to severe anaphylactic reactions. Allergy to hazelnut is frequently observed in patients with allergy to birch pollen.

Symptoms of food allergy in pollen-allergic patients are usually mild and restricted to the oral cavity, i.e. oral allergy syndrome. Allergy to hazelnuts without concomitant pollen allergy is less common, but symptoms tend to be more severe and are often systemic.

Allergies to peanut (a legume) and tree nuts (walnut, hazelnut, brazil nut, pecan) frequently have an onset in the first years of life, generally persist, and may account for severe and potentially fatal allergic reactions.

 

 

  f24 Shrimp

Allergen description

Pandalus borealis

Family

Crangonidae

Shrimp is found in shallow and deep waters everywhere. The largest of the species, mostly found in the Pacific, are called prawns.

Allergen exposure

Expected exposure

Meat from shrimps or prawns can be canned, breaded, frozen, sold in the shell or dried.

Some major shellfish allergens are heat-stable and water-soluble and can therefore enter the atmosphere in steam aerosols from the cooking process.

Unexpected exposure

Shrimp can also be an undeclared ingredient in some processed fish products and snacks.

Cross-reactivity

Common major allergens have been identified in shrimp, crab, lobster and crayfish. One of these allergens is tropomyosin, which is a major allergen in shrimp, but is also present in mites, cockroaches and other insects.

Of seven allergens detected, two appear to be shared by other Crustacea and one may be a specific allergen present only in shrimp.

Clinical experience

IgE-mediated reactions

Shrimp has been recognized as potent allergen both in food allergy and occupational allergy. While many children often outgrow allergy to cow’s milk and egg white, they may continue to be hypersensitive to shellfish later in life.

Shrimp allergy is common cause of anaphylaxis among adults. Other allergic reactions including urticaria, angioedema, respiratory symptoms and gastrointestinal problems have also been reported.

Shrimp-allergic patients often have respiratory allergy and shrimp is also an occupational allergen for seafood processors and workers in the fishing industry.

Food-dependent exercise-induced anaphylaxis after consumption of shrimp has occurred.