7 Common Food Allergies That Cause Eczema
Certain foods are known to trigger anaphylactic reactions in susceptible people. The hypersensitivity reactions caused by food allergies affect the gastrointestinal tract, the respiratory tract and the skin. On the skin, food allergies present as itching and swelling. The only solution is to avoid foods that may trigger your eczema. But how are food allergies linked to eczema? Who is likely to suffer from food-induced eczema and which food allergies can cause or worsen eczema? Read on to find out.
Food allergies are hypersensitivity reactions to certain proteins in foods.
Unlike other related (and sometimes confused) terms, the cause of food allergy is different from food poisoning (microbial toxins in bad food), food intolerance (inability to digest certain foods) or drug-like (because of the phytochemicals present in the food) pharmacological reactions to food.
Therefore, a food allergy must involve a protein and the immune system.
Often, a food allergy is triggered when protein fragments from the food resist digestion. To contain the damage caused by such protein fragments, the body quickly develops antibodies against them.
Usually, these undigested proteins are associated with immunoglobulins especially IgE. Once tagged, the body regards the proteins as foreign substances and always tries to eliminate them. This means that food allergies are usually life-long conditions and the best treatment is to avoid the food triggers.
The hypersensitivity response mounted by the immune system usually involves white blood cells sent to attack the offending proteins.
These immune reaction to allergenic foods usually affect the respiratory system, the gastrointestinal system and the skin.
When food allergies present on the skin, it occurs as dermatitis and can cause, worsen or increase the risk of atopic eczema.
Epidemiological studies show that the prevalence of food allergies among children is around 8% while 4% of adults are allergic to one or more foods. This means that some children do outgrow their food allergies.
Among children, protein food allergies are more common. In addition, children are more likely to be allergic to milk, meats, egg, seeds and nuts. In contrast, fish and shellfish allergies are more common in adults.
Food allergy can also be categorized by geography. For example, celery allergy is very common in Europe.
Often a food allergy is reported among societies that commonly consume such foods. For example, buckwheat flour allergy is common in Japan where the flour is used to make noodles.
On the other hand, high consumption of a certain food in a population may make it difficult to determine the prevalence of its allergy. A good example of this trend is corn allergy which is believed to be quite common in North America but not easily detected because corn is found in a lot of food products.
Studies show that eczema has a strong genetic component. One of the genes identified to be strongly involved in the development of eczema is the filaggrin gene.
The filaggrin gene is responsible for synthesizing the protein known as filaggrin. Filaggrin is a filament protein that binds to keratin in epithelial cells. This means that it is important for maintaining the structural integrity of the different layers of the skin.
A defect in the filaggrin gene is now known to raise the risk as well as severity of eczema.
In a 2009 review published in the British Medical Journal, the authors identified that filaggrin gene defects can be found in 10% of the population of North American and West Europe.
In addition, the researchers investigated the link between this genetic defect and the prevalence of food allergy, atopic eczema, allergic rhinitis, asthma and related immunological conditions involving hypersensitivity reactions.
By examining the results of 24 studies done on the subject, they found that
Another review published in the journal, Current Opinion in Allergy and Clinical Immunology in 2010 also confirmed that mutations in the filaggrin gene is strongly linked to atopic eczema.
This review also concluded that the increased skin permeability seen in people with filaggrin gene defect can contribute to the development of food allergies. The reviewers recommended that avoiding skin contact with allergens early in life can help prevent the development of food allergies and atopic eczema later in life.
Therefore, filaggrin gene defect can lead to early sensitization of the immune system even before it is fully developed.
Once the immune system tags an allergen, it can quickly establish allergic reactions against foods with that (or related) allergen.
Not all cases of eczema are caused by food allergies. However, food allergies, especially in children, are likely to trigger eczema and other related allergic diseases.
Because food allergies are not easily diagnosed, you may not know that your child’s eczema is caused by allergic reactions to certain foods. However, if you suspect food allergy or if the child’s eczema is not responding well to standard treatments, you may ask your doctor for food allergy tests.
There are different ways of determining food allergies. The most common method is skin prick tests.
Blood tests may also be ordered to look for specific antibodies against certain foods. However, both of these tests do not necessary provide a direct link between a food allergy and eczema. To establish such a link, you need oral food challenge.
Oral food challenge is simple and definitive but tasking. It requires giving the patient increasingly larger amounts of the foods suspected to cause eczema and then watching out for the signs of the skin conditions.
If the test food triggers itching, rash and/or swelling on the skin after a few hours of ingesting it, then a case of eczema caused by food allergy is diagnosed.
Discussed below are the 7 major foods known to cause or worsen atopic eczema.
Egg allergy is the second most common food allergy. Although it affects children more than adults, some people never outgrow it and it can persist as a lifelong condition.
Both egg white and egg yolk can trigger egg allergy. While some people are only allergic to the whites of eggs, some are allergic to the yolk and others can tolerate a little egg without experiencing hypersensitivity reactions.
Egg allergy can cause hives and skin inflammation. In severe cases, it may require emergency epinephrine injection to prevent the blockage of the respiratory tract.
Because some common vaccines are manufactured with chicken embryo, they may also contain egg proteins. Examples of vaccines that may contain leftover egg proteins include flu vaccine, MMR (measles, mumps and rubella) vaccine and yellow fever vaccine.
Since these vaccines are commonly given to children, there is a chance that sensitization can occur with vaccination.
Therefore, if your child experiences eczema flare-up after vaccination, there is a very high likelihood that egg allergy contributes to his eczema. If that is true, egg and foods prepared with it should be avoided in order to keep his eczema in remission.
Milk allergy is the most common food allergy among children. About 20% of children with milk allergy also suffer from meat (beef) allergy.
Studies show that about 3% of infants suffer from this allergy although most of them outgrow it. The prevalence of milk allergy among adults is about 0.5%.
There are a number of proteins that can trigger milk allergy. However, the most common milk protein responsible for this allergy is alpha S1-casein. Because this milk protein differs from one animal to another, there are different types of milk allergy.
Therefore, an infant with cow’s milk allergy may still tolerate breast milk and vice versa.
Milk allergy can cause a full set of anaphylactic reactions. It affects the skin as well as the respiratory and gastrointestinal systems.
On the skin, milk allergy can cause hives and rashes and it has been shown to trigger atopic eczema.
The onset of the allergic reaction to milk differs. While some experience it within minutes, it may take weeks to set in for other people.
It should be noted that milk allergy is different from lactose intolerance. While milk allergy involves a protein, lactose intolerance involves a carbohydrate. In addition, a lot more milk must be consumed for lactose intolerance to present with adverse effects. Milk allergy can be triggered by smaller amounts of milk.
Although wheat allergy is quite popular, it is not as common as milk and egg allergies.
Wheat allergy is really a term to describe a number of related but different food allergies. Scientists have identified 27 different allergens in wheat.
The most common wheat allergen is gluten. Gluten is a protein complex found in the endosperm of wheat and related grains such as oats and barley. It is composed of gliadin and glutenin.
The gliadin in gluten causes the most severe form of wheat allergy. It is associated with celiac disease and other chronic diseases caused by leaky gut syndrome. Through the involvement of the immune system, wheat allergy can progressively destroy the gastrointestinal mucosa as well as the layers of the skin.
Wheat allergy has been conclusively proven to cause eczema, atopic dermatitis and contact dermatitis.
This allergy is made even worse by aspirin and exercise as these factors increase the permeability of the gut mucosa and allow even more wheat proteins to enter into the blood.
Once in the blood, the immune system recognizes these antigens and launches exaggerated reactions that causes anaphylaxis and eczema.
Besides glutenin and gliadin, other wheat proteins that may cause allergic reactions include albumins and globulins.
Soy and soy products are especially rich in proteins. Examples of soy proteins are albumin and globulin. These proteins are also implicated in wheat allergy.
Other proteins in soy that may trigger allergic reactions include storage proteins such as legumin, vicilin and glycinin. Soy also contains digestive enzymes like papain and trypsin as well as hormonal proteins known as phytoestrogens.
Any of these proteins can trigger hypersensitivity reactions and worsen eczema. However, it is unlikely that soy allergy can cause eczema on its own.
One reason for this is that the amount of soy needed to be consumed to trigger soy allergy in susceptible individuals is very high (estimated at 100 the amount of other foods needed to trigger their allergies). Therefore, most people with soy allergy can still tolerate small amounts of soy proteins.
Even then soy allergy can cause severe, life-threatening anaphylactic reactions. When it triggers the release of IgE antibodies, the allergic reaction that results can cause itching and rashes on the skin.
Peanut allergy is different from tree nut allergies because peanut is a legume and not a true nut.
This form of food allergy affects about 1% of the population but it can cause severe anaphylactic reactions. Although most of the hypersensitivity reactions of peanut allergy involve IgE, anaphylatoxins are also involved.
This latter part of the hypersensitivity reaction causes the release of histamine from the mast cells of the immune system.
In the respiratory tract, histamine causes the constriction of the airways. However, in the skin, it causes severe itching.
Besides simply triggering hives, peanut allergy has been shown to worsen atopic eczema.
Seafood allergy is a broad term used to describe allergic reactions to the proteins found in scaly fish, shellfish and crustaceans.
Although it mostly affects adults, seafood allergy can also affect children. In fact, people who suffer from the allergies discussed above are likely to also have seafood allergy.
Seafood allergy can be triggered by other means besides consuming seafood. There are cases where handling seafood or exposure to the cooking odors of seafood have triggered the allergy.
Seafood allergy can cause serious physical symptoms and may require emergency epinephrine injection.
Besides anaphylaxis, seafood allergy can trigger rashes, itch and other cutaneous presentations of eczema.
Meat allergy is a rather curious food allergy. For one, it is triggered by a carbohydrate rather than a protein.
In addition, sensitization to this allergy occurs from a tick bite. The tick responsible is Amblyomma americanum or lone star tick. Therefore, meat allergy is mostly reported in central and southern United States.
Once sensitized, the sufferer becomes sensitive to alpha gal (galactose-alpha-1,3-galactose). Alpha gal is a carbohydrate found only in the meats of mammals.
Allergic response to alpha gal is usually delayed. Therefore, unlike most food allergies, meat allergy is a delayed (4 – 8 hours) hypersensitivity reaction. However, it involves IgE too.
Meat allergies can trigger the appearance of hives on the skin as well as eczema-like swelling.
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