Ige Mediated Peanut Allergy Development Diagnosis And Treatment Biology Essay

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Severe peanut allergy, known medically as IgE-mediated peanut allergy, is a growing problem in our society. In order to comprehend the seriousness of peanut allergy, it is important to understand some food allergy basics. The difference between a food allergy and an intolerance, and the biological development of a food allergy falls among this. Although not completely preventable, certain factors cause some individuals to be more allergic than others. There is a fairly recent school of thought, called the "hygiene hypothesis" which postulates that increased hygiene and lack of exposure to microorganisms may be affecting the immune systems of many individuals. This paper will also explore the symptoms of anaphylactic shock and the role of epinephrine to combat it.

Sean is a happy and energetic 3-year-old boy. He appears completely healthy and normal to everyone around him. However, last week Sean was at a birthday party and ate a piece of cookie that his friend shared with him. Sean has a peanut allergy. The accidental ingestion of that cookie resulted in a severe allergic reaction, in which a very visible red, itchy rash instantly spread across his face, neck, chest, and arms, in which his face, lips, and tongue swelled almost beyond recognition, and he began to have trouble breathing. Thankfully, a quick shot of medicine into his quadracep muscle and a trip to the emergency room was able to save his life.

Many find it hard to comprehend that the ingestion of even trace amounts of a particular food could cause a reaction severe enough to threaten a person's life. It is almost unimaginable that food, which we depend on not only for our sustenance, but for a majority of our social activities as well, could pose such a threat to those who suffer from food allergies. However, many do suffer. In fact, it is estimated that 12 million Americans, 3 million of whom are children, have food allergies (The Food Allergy & Anaphylaxis Network [FAAN], 2011; American Academy of Allergy Asthma & Immunology [AAAAI], 2011). Milk, eggs, nuts, and seafood are the most common food allergy culprits among American children, and peanut allergy in particular has more than doubled in children from 1997-2002. Although the majority (95 percent) of peanut allergic patients can safely eat soy or beans, which are also legumes, many (25 percent) have a concurrent allergy to tree nuts such as pecans or walnuts. Within the confines of peanut allergy alone, one in five allergic reactions to peanuts are Anaphylactic, accounting for approximately 47,000 cases, 184 of which were fatal, in 2008 (AAAAI, 2011). These statistics are alarming, which is why it is imperative not only to understand allergies in general, but to understand the biological development of them as well, noting that the scope of this paper will focus specifically on severe peanut allergy. Furthermore, the result of a severe peanut allergy is often anaphylactic shock, which is combated through an injection of epinephrine. Finally, due to current research being done surrounding the reason as to why allergies have increased in recent years, a look will be taken into the leading hypothesis surrounding the cause of food allergy.

What Is Food Allergy?

Food Allergy vs. Food Intolerance

Food allergy is an abnormal response to a food that is triggered by the body's immune system and causes hypersensitivity. Allergic reactions can cause, in its milder reactions, vomiting, cramping, diarrhea, an itchy mouth, lip swelling, and hives. In its more severe forms it can cause throat tightness, wheezing, obstructive tongue swelling, trouble breathing, and loss of consciousness (Li, 2009; Sicherer, 2006, pp. 4-15).

This however, is different than food intolerance. In a situation of food allergy, there is a system of steps within the immune system that causes a person's body to respond abnormally. Although this will be reviewed in a later section, on a basic level, the immune system mistakenly identifies a food protein as a foreign and harmful substance and responds by producing an antibody to fight the said protein. This results in a release of chemicals into the bloodstream and can cause the symptoms noted above (Campbell, Reece, Taylor, Simon, & Dickey, 2009 p. 501).

Food intolerance, on the other hand, does not usually involve the immune system. Some common food intolerances that are often confused for allergies are as follows: Irritable Bowel Syndrome, which causes chronic diarrhea; a sensitivity to food additives, such as those in wine or in preserved fruit; an absence of an enzyme required to digest a food, such as lactose intolerance; and Celiac disease, which stems from the inability to process wheat products (Li, para. 5).

Biological Development of Food Allergy

The Role of the Immune System

The immune system defends the body against infections, such as those caused by bacteria, viruses, parasites, and fungi. Essential to its health, is its ability to discriminate between the body's own cells-self-and foreign cells-non-self. When the body is exposed to such foreign invaders, called an antigen, the immune system generates antibodies specific to that which it was exposed to. These antibodies bind to the particular antigens it was produced for and attacks them. This antibody production allows the body to effectively fight against a future invasion from the same antigen (Playfair & Chain, 2005, pp. 74-75).

Abnormal immune response. Sometimes, an abnormal reaction can occur, such as when the immune system mistakes self for non-self cells, and therefore attacks its body's own cells. This is called an autoimmune disease. Another abnormal reaction can occur when the immune system reacts to an apparently benign foreign substance, such as the protein from a food, as if it was a germ, or produces antibodies, specifically those referred to as Immunoglobulin E (IgE), to combat it. This food protein is called an allergen. The IgE antibody reacts to the allergen, such as peanut protein, by attaching itself to the immune system's mast cells which in turn release histamine and other chemicals which trigger the inflammatory response. This is considered the first stage of food allergy development, called sensitization (Playfair & Chain, 2005, pp. 74-75; Campbell, Reece, Taylor, Simon, & Dickey, 2009, p. 501). Because mast cells are found throughout the body-in the skin, mucous membranes, and gut, symptoms can be widespread and can manifest themselves in a variety of ways (Fitzsimmons, p. 39).

Future exposure and histamine release. When an individual is exposed to the allergen again, the release of histamine can often become more prevalent, resulting in a quicker and more serious onset of symptoms. It is important to note that these symptoms may range in scope from mild to severe-even fatal. The immune system's heightened response and confusion of an allergen to a more detrimental antigen can cause some food allergic individuals to develop more severe reactions over time. What may start out as an itchy mouth and mild rash can eventually develop into Anaphylaxis (Fitzsimmons, 2010, para 4; Yunginger, 1988).

Non-IgE-Mediated Food Allergy. The immune system attacks foods in other ways than through IgE antibodies. In fact, it is important to note that a multitude of cells and chemical messengers protect the body from infection. One such cell is the T cell; this is the army general, so to speak, of the immune system. Its role is to direct various cells to various locations within the body when a foreign substance is found. In regard to allergy, the T cell releases signals that direct a specific type of immune cell called the eosinophil. Eosinophils are responsible for allergic inflammation, and inflammation is the main feature of chronic allergic diseases such as eczema and certain chronic gastrointestinal diseases. It is thought that the eosinophils, like IgE antibodies, are important in the battle against parasites. When eosinophils arrive at the site of the foreign food protein particle, they release chemicals. These reactions do not cause the same life-threatening symptoms as IgE-mediated allergies; rather they often cause severe and chronic skin rashes, diarrhea, and poor growth. The problems caused by a non-IgE antibody food allergy can be corrected once the problem food is identified and eliminated from the diet (Jyonouchi, 2008; Sutton, 2007, p. 3-11).

Prevention of IgE-Mediated Peanut Allergy

Risk of Allergy

The allergic diseases, asthma, eczema, hay fever, and food allergy, tend to run in families and occur in the same individuals. This is because these are the inherited disorders of a gene mutation. In fact, according to a 2000 report from the American Academy of Allergy, Asthma, and Immunology (AAAAI), if one parent has an allergic disease, regardless of the type, there is a 50 percent chance that that his or her child will have an allergy as well (as cited in Sutton, 2007, p. 26). If both parents have allergies, there is an estimated 80 percent chance that their child will have allergies (Cavendish, p. 193). Given that these diseases affect 40 to 50 million people-more than 20% of the population-a considerable portion of our population is at risk for developing an anaphylactic response to peanut (AAAAI, p. 4).

Rise in Food Allergies

Genetic predisposition, however, does not necessarily mean an allergic sensitivity will occur. A large portion of food allergies are dependent on genetics, but exposure is also a variable that must be accounted for. Although some studies cite that a pregnant or breastfeeding mother's diet can affect the fetus and nursing infant in regard to future peanut sensitivities, and that and that early exposure of certain foods to infants can cause allergy, there is an equal number of studies that indicate otherwise (Hourihane, 1997; Lack, Fox, Northstone, & Golding, 2003). Nevertheless, in a five-year period from 1997 to 2002, the rate of peanut allergy in American children increased from 1 in 250 children to 1 in 125. Similar results have been seen in other highly developed, westernized countries, such as England (American Peanut Council & The Peanut Institute, n.d., p. 2).

The question raised by this startling statistic is whether medical professionals are better at diagnosing and advocating for the issues surrounding food allergies, or is there is a true increase? Multiple studies indicate that our immune systems are over-reacting and attacking harmless proteins at a higher rate than before. Scott Sicherer, is a professor of pediatrics, allergy and asthma at the Mount Sinai School of Medicine, and a world-renowned expert in the subject. He cites in his book Understanding and Managing Your Child's Food Allergies, that numerous studies have shown, through allergy tests on the general population, without selection for people with specific allergy-related complaints, that positive tests have more than doubled within the past two decades (p. 254). Because heredity does not change that quickly, it must be considered that environmental changes are contributing forces in food allergy, and peanut allergy in particular (Campbell, Reece, Taylor, Simon, & Dickey, 2009, p. 264). The primary theory to explain this increase is called the hygiene hypothesis.

The Hygiene Hypothesis. The body's immune system is designed to fight infections such as parasites, viruses, and bacteria. As noted earlier, IgE antibodies and eosinophils, certain parts of our immune system that cause allergy are also responsible for fighting of parasitic infections. The United States and other well-developed countries do not have a problem with parasitic infections. The hygiene hypothesis maintains that because this part of the immune system is often not needed, it attacks otherwise harmless proteins, such as those found in peanuts (Sutton, 2007 p. 62-63; Sicherer, 2006, p. 255). The hypothesis also states that developed countries have reduced much of the need for the immune system to fight infections on its own. Antibiotics are readily available and many vaccinations are required by schools and employers. Western culture has also become more and more concerned with cleanliness, such as hand-washing, wearing shoes, and keeping a clean home. This allows for a variety of germs to be removed from our environment. This lack of exposure is what gives much of the hygiene hypothesis its fuel. Basically:

The more hygienic one becomes, the more susceptible one is to various autoimmune diseases. . . . The hygiene hypothesis, [which is not yet proven], acknowledges that the maturation of the immune system needs some kind of hardening, some kind of resistance. Put another way, [a body] cannot really build up good muscles without doing exercise (as sited in Sutton, 2007, pp. 61-62).

Allergy Test for IgE

Skin Prick Test

Because mast cells are found throughout the body, including the skin, the skin prick test is able to challenge those armed with the IgE antibodies that are geared toward the proteins in food through a fairly simple procedure. A skin prick test utilizes a small plastic probe with sharp tips. These tips are used to scratch the skin with a diluted extract of a suspect allergen, such as a peanut protein. If an IgE-mediated allergy is present, histamine will be released by the mast cells when it comes into contact with the pricked area of skin. This will cause a bump, called a wheal, surrounded by a red ring, referred to as a flare. As a comparison against whatever allergens are present, two tests are performed: a saline test and a histamine test. Because some individuals develop some swelling where they are scratched, called dermographism, a saline scratch is used as a control. The histamine scratch will cause a wheal-and-flare, the size of which allows for a comparison of reactions caused by the food allergens that are being tested (Roberts & Lack, 2005).

It is important to note that a positive test result does not necessarily mean an individual will have a guaranteed type of reaction. Instead, it means that an antibody for the allergen, such as peanut, is present in the blood (Roberts & Lack, 2005). However, the size of the reaction, based upon wheal size is useful in predicting severity (Finkelman, 2010).

Anaphylaxis

What is Anaphylaxis?

Anaphylaxis is a severe allergic reaction, and it can be fatal. The entire body is affected, often within minutes of exposure. Peanut allergy frequently causes the most severe reactions (Finkelman). Because IgE-mediated allergy symptoms occur on a spectrum, it is vital to be able to distinguish between those which are not harmful, but uncomfortable, and those that are already, or may quickly become, life threatening. The following information, as presented by Sicherer (2006, pp. 14-15), is useful in this context:

Examples of Anaphylactic Symptoms That Are Not Necessarily Life Threatening

Breathing Nasal congestion

Runny nose

Occasional cough

Gastrointestinal Nausea

Vomiting

Diarrhea

Abdominal pain

Itchy mouth/ear canal

Lip swelling

Odd taste in mouth

Skin Flushing

Itch

Skin (continued) Hives

Skin swelling

Eczema flare

Other Red/itchy eye

Uterine contractions

Each symptom in the following list, may, by itself, indicate a more life-threatening symptom that could already reflect impaired breathing or circulation, or that they may soon be compromised.

Examples of Anaphylactic Symptoms That Are or May Soon be Life Threatening

Respiratory Throat tightness

Wheezing

Shortness of breath

Repetitive coughing

High-pitched noises when air goes in and out

Change in voice

Turning pale/blue

Gastrointestinal Obstructive tongue swelling

Trouble swallowing

Cardiovascular Low-blood pressure

Fainting

Chest pain

Dizziness

Weak pulse

Other Feeling of "impending doom"

Treatment of Anaphylactic Shock

Due to anaphylaxis' vasoconstrictive effects, epinephrine is the principal medication used in response to such shock. Epinephrine, also known as adrenaline, is a hormone that prepares the body for action by boosting oxygen to the brain and muscles, while suppressing other non-emergency functions such as digestion. The immediate recognition of anaphylaxis and its treatment are imperative to combatting death (Sutton, 2007, p. 46).

Unusual Food Protein Exposure

Peanut-induced anaphylaxis is a very real threat for those who suffer from such a severe form of the allergy. A meticulous attention to detail must be had to avoid peanuts in the diet. To further anxieties, although rare, there are instances in which an anaphylactic reaction has occurred through means other than ingestion.

Airborne Exposure

Food allergens can become airborne. However, the belief that it is the "odor" of peanuts that causes an allergic reaction is not true. It must involve the inhalation of microscopic protein particles in the air. However, many allergic individuals have reported symptoms of difficulty breathing, tightness in the chest, skin rashes, and itching-all from being within the same room as peanut products (Young, 2003). As a result, many studies have been conducted using peanut butter-an oily substance, with peanut allergic individuals in real-life settings. According to one study, in particular, no airborne peanut proteins were visible, and regular household cleaning products effectively removed all trace amounts of peanut off tables, faucets, and the like (Perry, Conover-Walker, Pomes, Chapman, & Wood, 2004). Raising question to the methods of the study however, is the fact that many peanut products are highly refined, especially that of peanut butter. Refinement of peanut products also varies by type of product and brand, and many gourmet peanut products are unrefined and have been proven to result in considerably higher airborne protein levels (Young, 2003; Hourihane, 1997).

Exposure through Kissing

It must also be recognized that if an individual without a peanut allergy ate something with peanuts in the ingredients and then passionately kissed someone severely allergic to peanuts, saliva containing the allergen would most likely be transferred by mouth. Studies have shown that among adults with severe food allergy, approximately 5 percent have experienced allergic reactions from kissing. Casual kissing, such as that on the cheek, is much less likely to result in the same way (Sicherer, 2006, p. 155)

Conclusion

Severe peanut allergy, although similar to other Ig-E mediated food allergies, is unique in its scope because of the higher rate of severe allergic reactions and the potential for reactions due to airborne exposure. Individuals suffering from severe peanut allergy must life a lifestyle different than that of the non-allergic; awareness, not only about product ingredients, but also about the different symptoms of anaphylaxis, lead to constant vigilance. Although there is a multitude of research being conducted surrounding cures for Ig-E food allergies, which this paper did not address, the hygiene hypothesis, with an eye toward prevention appears to be most promising. After all, understanding the role of the immune system in relation to our ever increasing "clean" environment, may not only reduce the rates of food allergy, but may also assist in other disorders of the immune system.

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