Common Allergies

Horse Allergy

Patients often overlook and mistake allergy to horses, for allergy to pollens or molds. These patients are usually allergic to horse hair and dander. Treatment for this allergy would include medications, horse avoidance and/or allergy immunization to decrease the sensitivity to horse allergen. Horse allergies are especially potent due to the size of the animal and the volume of dander they generate.

Rabbit Allergy

Patients most often suffer this allergy from exposure to rabbits in their daily work. The The most common people at risk are veterinarians, laboratory technicians and pet owners. The rabbit's saliva and fur are the common allergens.

Cat Allergy

Patients allergic to cats, are allergic to the cat's saliva. However, typical allergic symptoms are not as a result of coming in direct contact with the cat's saliva. Instead, when the cat grooms itself by licking its fur and skin it deposits its saliva. They saliva dries, leaving behind the protein antigen that are the source of allergy to cats. These allergens (cat saliva antigens) are very light-weight and are easily aerosolized. Once air-borne the antigen can spread to clothes, furniture, carpeting, or any other household item.

Once cat allergy is confirmed, the best way to decrease allergy symptoms is to remove the cat from the home. However, relatively high concentrations of cat antigen can remain, even months after the cat is removed. Thereby it is important to clean or replace the carpeting, furniture, and all other material that may harbor the cat saliva antigen.

Thankfully, there are less dramatic means to improve or eliminate cat allergy symptoms as well, including the use of medications and allergy immunization. HEPA (high efficiency particulate air) filters can catch particulates as small as one micron, and are effective in combating cat allergens.

Dog Allergy

Patients allergic to dogs, are allergic to the dog's saliva. However, typical allergic symptoms are not as a result of coming in direct contact with the dog's saliva. Instead, when the dog grooms itself by licking its fur and skin it deposits its saliva. They saliva dries, leaving behind the protein antigen that are the source of allergy to dogs. These allergens (dog saliva antigens) are very light-weight and are easily aerosolized. Once air-borne the antigen can spread to clothes, furniture, carpeting, or any other household item. Allergy to dogs is not as problematic as allergy to cats, primarily because:

• Dogs are usually kept outside
• Dogs are kept outside of bedrooms
• Dogs are washed regularly

Once dog allergy is confirmed, the best way to decrease allergy symptoms is to remove the dog from the home. Also, there are less dramatic means to improve or eliminate dog allergy symptoms, this includes the use of medications and allergy immunization. HEPA filters can catch particulates as small as one micron, and are effective in combating dog allergens.

Allergic owners should not be involved with the washing or grooming of the dog.

Rodent Allergy

Patients become allergic to rodents due to exposure to these animals in their daily work. The most common people at risk are veterinarians, laboratory technicians, and people who live in close quarters with rodents (such as pet owners and those who live in rodent-infested homes).

Some example of common rodent that humans come in contact with include mice, rats, and guinea pigs. The rodent's urine has a high concentration of protein, which is the primary allergen to humans. The urine is often sprayed rather than deposited, thereby increasing human exposure. After the urine dries, the urinary proteins become air-borne and are inhaled, leading to allergic symptoms.

The use of HEPA filters is the most effective way to combat rodent allergies. There is currently no immunotherapy against this type of allergy.

Dust Mite Allergy

Dust mites are approximately 0.3 mm in length, too small to be seen with the naked eye. They are eight-legged and sightless, and live on skin scales and other debris. Mites excrete partially digested food and digestive enzymes as a fecal particle, which release allergens very rapidly. Most patients allergic to dust mites are actually allergic to the dust mite feces.

The mite fecal pellets are similar to pollen grains in three major ways:

• The fecal particles size
• The quantity of allergen carried
• The rate of proteins release

By being so similar to pollen grains, they are just the right size to cause allergies. Dust mites become a part of our environment and lifestyle because of their natural adaptations. Since they are entirely dependent on ambient humidity for hydration, and they are unable to search for environmental water supplies, they tend to live in places that "store" water. This may include carpets, sofas, mattresses and clothing. As humidity falls, mites withdraw from the surface and migrate to where there is more humidity; e.g., deeper in the mattress. Even in very dry conditions it may take months for mites to die and for their allergen levels to fall.

Avoiding contact with dust mites is the best way to protect against dust mite allergies.  This can include the use of dust mite covers on bedding, as well as HEPA or statically charged air filters (HEPA filters are typically more effective in combatting dust mites).  Immunotherapy, allergy shots and even over-the-counter antihistamines can help sufferers.

Allergy to Stinging Insects

When a person is stung by a bee, wasp, hornet, yellowjacket or fire ants, the insect injects venom into its victim. This venom can cause severe life-threatening reactions in certain people who are allergic to it. In a typical reaction, the sting site will be painful, reddened, and may swell and itch, but this will only last a few hours. Enlarged local reactions might be seen with a painful swelling of several inches surrounding the area of the sting. This reaction might last for days.

In a severe allergic reaction the person might feel dizzy, nauseated and weak. Stomach cramps and diarrhea may occur. Generalized hives and itching, wheezing and difficulty breathing, and potentially an anaphylactic reaction with a sudden drop in blood pressure, loss of consciousness which may lead to death can occur if no immediate medical care is provided. In a majority of patients, venom immunotherapy will protect against any future life-threatening reactions. In the case of severe or generalized reactions, patients with known allergic sensitivities to insect venom should be evaluated by an allergist and placed on protective desensitization therapy.

Cockroach Allergy

Roaches, especially the German Cockroach, are a very common pest in crowded cities worldwide. Recent studies have shown exposure to roach droppings as a major risk factor for the development of allergies and asthma in the inner-city. Avoidance consists of roach baits and traps, extermination and cleanliness. This includes, not leaving food out in open containers, washing dishes after each meal, and keeping cupboards free of food debris. Unfortunately, one can't encourage cleanliness in their neighbors! Patients who are not responsive can be treated with medications and allergy immunization.

Food Allergies

Food allergies are based on specific food protiens, and are not to be confused with food intolerances (such as lactose).  Those suffering from food allergies are advised to read food labels carefully, and always have an EpiPen (a brand of epinephrine injector) handy in case of an incident.

Milk

Patients with very sensitive milk allergy can react to even a very small quantity of milk protein, including minor contamination or inhalation of milk powder. Milk is  found in a large variety of processed foods, some obvious and others not.  These products include confections, margarine, cheese, and pies (see table below). Cheese and cream contain milk protein and should be avoided. Milk contamination of a product is possible if the same manufacturing equipment is used for multiple products. In addition, patients should be careful when ordering sliced products from outlets that use the same slicers for cutting a variety of foods (e.g., cheese and cold cuts). Lactose, a milk sugar, may contain residual milk protein.  Lactose is found in a variety of foods and is also used a filler in medicines such as Benadryl capsules.

Hypoallergenic milk formulas have been used as a milk replacement for children with milk hypersensitivity. However, hypoallergenic milk formulas are not nonallergenic, and many children react to these, depending on the particular formula.

Common descriptions on ingredient panels are milk, pasteurized milk, full cream milk powder, dried milk, and skim milk powder (see table below). Extracted milk proteins added to foods retain their antigenicity and may be described as casein, caseinate, whey or whey powder. Many individuals consider skim milk and skim milk powder not to be milk and substitute these for milk. In some instances milk is used in emulsions and can be described as caseinate, emulsifier or protein

Allergy to Eggs

Egg is one of the most allergenic of all foods, and minute amounts of egg can result in symptoms within minutes, including life-threatening anaphylaxis. This is also seen after contact with egg through non-oral routes. Reactions may occur the first time a child is given egg.

Although ovalbumin, ovomucoid, and ovotransferrin have been identified as the major allergens in egg white, 10 other unnamed allergens of lesser importance have been identified. These allergens are also present in egg yolk but in lesser quantities. This is important because components of egg may be individually used for specific actions in food preparation. For example, hen's egg lysozyme is used as a preservative in food; and in some countries, notably Japan and Switzerland, lysozyme is used in medications. Individuals sensitive to hen's egg have been shown to be allergic to lysozyme produced from hen's egg.

A variety of descriptions may indicate the presence of egg protein in a product. The function that egg performs in a product may be named on the ingredient panel (e.g., binder, emulsifier, or coagulant). Because legislation may permit a manufacturer not to list an ingredient constituting less than a specific percentage of the total product, noodles containing egg may not have egg listed on the ingredient panel. A similar situation may occur when egg white is used to give pretzels, bagels, and other baked goods their shiny appearance. In most products, lecithin is derived from soy, but sometimes it may be egg-derived. Provitamin A (extracted from egg) may be used and described as a colorant, but its antigenic properties are unknown.

In addition to food products that may be dangerous to egg-sensitive individuals, egg proteins are also found in cosmetics, shampoos, and pharmaceuticals, such as the laxative Agarol. A patient allergic to egg should avoid buying fried foods from vendors who use the same frying surface for preparing multiple types of food. Recent evidence suggests that egg-sensitive children can receive measles immunization safely.

Although rare, avian proteins can induce egg allergy in susceptible individuals. It has been suggested that duck egg be substituted for hen's egg in egg-sensitive individuals. These individuals are able to tolerate cooked chicken.

Allergy to Nuts (not peanuts)

Tree nuts are generally cross-reactive. If one is allergic to a variety of nut, he or she should try to avoid all of them. The list of common tree nuts include almonds, Brazil nuts, cashews, hazelnuts (filberts), macadamia nuts, pecans, pine nuts, pistachios and walnuts. Peanuts are not included in this group, as they are not technically nuts (but, rather, legumes). Anyone with a nut allergy, however, should be cautious because they may be processed alongside actual nuts.

Allergy to Peanuts

Peanuts are one of the most allergenic foods, and peanut allergy is one of the most common food allergies. Peanuts are probably the most common cause of death by food anaphylaxis in the United States, and about one third of peanut-sensitive patients have severe reactions to peanuts.

Peanuts are added to a large variety of processed foods (see first table). These include ice cream (as a flavoring), marinades, snack foods and biscuits. Peanuts can be used as a flavoring or a seasoning agent and may be labeled as such (see second table). Peanuts may be used in the manufacture of vegetable burger patties. A fatal reaction to peanut antigens in almond icing has been recorded. Peanut butter may also be used to glue down the ends of egg rolls to keep them from coming apart. Additionally, it is not widely known that peanut butter is commonly used in Asian cuisine. Peanuts can be deflavored, reflavored, and pressed into other shapes such as almonds and walnuts. These products retain the allergenicity of the peanut. Some patients with peanut allergy also react to sweet lupine seed flour, which may be used, for example, to fortify pasta.

Although uncommon, a peanut protein hydrolyzate may also be used in soft drinks as a foaming agent or in confections as a whipping agent.

Peanut oil is frequently used in the preparation of health foods. The oil can be used for many non-food products, which may, on contact, affect sensitive individuals. Like peanut oil, other vegetable oils such as soy, maize, sesame and sunflower oils contain very low quantities of protein.

Peanut oil has been considered to be devoid of allergenicity, and this was initially confirmed by double-blind crossover studies. However, peanut oil allergenicity is clearly process-related, because cold-pressed peanut oils may contain peanut allergen. Moneret-Vautrin et al. confirmed the allergenicity of peanut oil in milk formulas, and 11 of 45 brands of milk formulas in France contained variable amounts of peanut oil. Residual peanut proteins are believed to become more allergenic with heating.

A recent study showed that 50% of individuals allergic to peanuts (a legume) reported allergic reactions to other tree nuts as well, often because the foods are processed and shipped together.  These findings were not validated by further clinical investigation.  For patients whose allergies are limited to peanuts, nuts such as almonds, pecans, or walnuts can be used as a substitute.

Both ImmunoCAP and epicutaneous testing can help confirm peanut allergies in patients.

Allergy to Wheat Products

Wheat is the most allergenic of all cereals. IgE antibodies have been found in many components of wheat kernels, including albumin, globulin, gliadin, wheat germ agglutinin, a concanavalin A-purified glycoprotein, and a trypsin inhibitor. Wheat is most rich in gluten, with the other grains containing a lesser mixture of gluten and gliadin.

In addition to being present in all wheat-based food products, wheat gluten is frequently added to baked products made from other grains, including those made from soy flour.

Wheat-sensitive individuals should avoid a product that includes other flours, because it is likely that at least some wheat flour or a derivative will also be present. Even gluten-free bread may contain small amounts of gluten (0.4 mg per 30 gm slice). Bread wheat, durum wheat, triticale, rye and barley, to a lesser extent, are the main gluten-containing cereals. Others include semolina, spelt, and kamut. Cereal products, such as couscous and graham flour, are also prepared from wheat. Spelt has occasionally been marketed as a wheat alternative but is actually part of the wheat family. Spelt may better be described as non-hybridized wheat. No data have indicated differences in the allergenic profiles of the various wheat varieties, and they should all be viewed as potential allergens.

Hydrolyzed wheat proteins can be used in processed foods for flavoring purposes (e.g., in meat flavorings) or as a binder in vegetarian burgers. In the United States legislation dictates that this form of wheat must be labeled as wheat-derived, but this is not always the case in other countries. Wheat can appear under various names on ingredient panels (see first table) and can be found in many food products (see second table). Gluten finds its way into a few pharmaceutical products (e.g., Dimetapp LA, Nulacin, and Fybranta).
Buckwheat is not a member of the grass family and is thus not a true cereal. The grain may be used for human food in various forms from pancake flour to buckwheat noodles and baby foods.

For the wheat-hypersensitive individual, products made from oats, rice, rye, barley or corn or speciality foods made for gluten-sensitive individuals generally may be used instead of wheat. However, cross-reactions, although unusual, may occur between wheat, barley, rye, maize and rice.

Coeliac disease is a disorder of the small intestine, caused by a reaction to a gluten protein appearing in wheat, rye, oats, spelt and barley.   Symptoms include chronic diarrhea and fatigue.  Note that, while triggered by wheat, the disease is not the same as a wheat allergy.  Coeliac disease – also called coeliac sprue – is determined with blood testing.  A gluten-free diet remains the only defense against this condition.

Allergy to Fish

Fish is one of the most common causes of food allergy, particularly in adults and in Scandinavian countries. Fish may find their way into processed foods in raw, powder or oil form. In the majority of instances, this substance is clearly labeled as “fish” or with another obvious descriptor. However, fish allergens may be go unlisted if added as part of an oil. Fish products are not usually hidden ingredients but can go unspecified in Caesar salad dressing or in Worcestershire sauce if it contains anchovies.

Some seafood flavors (e.g., shrimp) are added to food in the form of a powder manufactured from the seafood's shell. Shrimp antigen II is heat stable. A variety of antigens are shared by several crustaceans including shrimp, prawns, crabs, lobsters and crayfish (crawfish). These antigens are not eradicated by cooking.

At present, some manufacturers are researching the possibility of adding fish meal (flour) to bread as a source of omega-3-fatty acids (personal communication, M. M. Melnyczuk).  Skin prick tests and RASTs indicate extensive cross-reactivity among fish species, but recent research suggests that patients may be able to consume some species of fish despite positive test responses to one or two. However, it is generally recommended that patients allergic to fish avoid all fish species.   An epicutaneous test can confirm a fish allergy.

Allergy to Shellfish

Shellfish, or crustaceans are generally cross reactive. If one is allergic to one, one should try to avoid all of them. The list of includes:

Fish are not included in this group. Anyone with shellfish allergy, however, should be cautious, because fish and shellfish may be processed together.

Allergy to Soy Products

Soy is so widely distributed in processed foods that avoidance of soy in one’s diet is very difficult. Thus, it is a particularly insidious hidden allergen. As with many other allergens, reactions may occur to very small quantities of soy protein, and anaphylaxis to soybean protein has been reported. Soybean lectin is also an important allergen and has been associated with allergic reactions.

Soybeans may be ingested as whole beans, as flour or as oil. In addition, soy can be used in the manufacture of food in a vast variety of ways, including as a texturizer, emulsifier and protein filler. Soy may thus be listed on the ingredient panel according to its use, e.g., hydrolyzed protein or lecithin (see table below).

Soybean flour is often added to cereal flour and is used extensively in the baking industry. The majority of breads contain some soy flour. Pastries, cakes, biscuits and baby foods may contain soy flour. It is also used in the manufacture of sausages, processed meats, hamburgers and other meat products. Fermented soybean may be used in the preparation of soy sauce or Worcestershire sauce. Fermented soy is in wide use as a food in the Far East.

Soy may also find its way into a food product when added as a compound ingredient. For example, if margarine is added to a food product it will be listed as such, but soy present in the margarine itself will not be listed on the ingredients panel.

Soy protein isolate or concentrate may be used to emulsify fat in food products and may thus be used in the manufacture of ice cream, mayonnaise, and a variety of other liquid fat- or oil-containing foods. The concentrate or isolate may also be used in soymilk and as a protein concentrate added to health foods and high-protein biscuits. Other foods that may contain soy include pureed and cereal baby foods, margarine, and white and brown bread.

Other uses for soy include the manufacture of tofu (soybean curd), which may in turn be used for the manufacture of soy-based ice cream. Soy may be converted into products having a meat-like texture. This textured vegetable protein is used in simulated meat products or may be added to meat as an extender. These products are often used as meat substitutes in vegetarian products and in catering establishments, including hospital and army food services, and feeding programs.

The seeds of soybeans are widely used as a source of oil. The oil has many uses. e.g., in salad dressings, margarine, baby foods, industrial components, linoleum, paint, plastics, soap, and glue for plywood (see table below). Although soybean oil was initially thought to be safe for soy-sensitive individuals, it is now evident that soy protein may occur in soybean oil. Thus the allergenicity of soybean oil would depend on its purity, which in turn depends on the extraction process. Recent evidence has demonstrated that although oxidized soybean oil may not show allergenicity, proteins in soybeans are capable of interacting with oxidized lipid to form products that are allergenic to soybean-sensitive patients. Indeed, Hiyama et al. report a case of urticaria associated with parenteral nutrition with an intravenous 10% lipid emulsion containing a soybean oil base. Such reactions, however, appear to be uncommon, and there are very few reports of this nature in the literature.  

Soy products are often purchased by those specifically avoiding cow's milk, often with the assumption that a soy-based product is free of cow's milk protein. This may not always be true, and caution is recommended. Again, labels should be read carefully, and they should, of course, contain the correct declaration.

Thickeners, stabilizers, emulsifiers and bulking agents may be manufactured from a variety of other members of the legume family in addition to soybeans. On the basis of in vitro studies, Barnett et al. suggests there may be cross-reactions between soy and other members of the legume family (see table below). Further evidence for broad cross-reactivity has been provided by RAST and skin prick tests; however, it is rare to have symptomatic reactivity to more than one member, and clinical hypersensitivity to one legume does not require elimination of the entire legume family. Carob, derived from the carob bean, is used commonly as a chocolate substitute, and one should possibly guard against cross-reactivity to this legume.