Peanut allergy

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Peanut allergy
Classification and external resources
Peanut allergy warning
ICD-10	T78.4
ICD-9	V15.01
DiseasesDB	29154
MeSH	D021183

Peanut allergy is a type of food allergy distinct from nut allergies. It is a hypersensitivity to dietary substances from peanuts causing an overreaction of the immune system which in a small percentage of people may lead to severe physical symptoms. It is estimated to affect 0.4-0.6% of the population.^[1] It is usually treated with an exclusion diet and vigilant avoidance of foods that may be contaminated with whole peanuts or peanut particles and/or oils. The most severe peanut allergies can result in anaphylaxis,^[2] an emergency situation requiring immediate attention and treatment with epinephrine.

Contents 1 Symptoms 2 Causes 3 Prevalence 4 Treatments 4.1 Oral desensitization 5 Allergen-free peanuts 6 See also 7 References 8 External links

[edit] Symptoms

Symptoms of peanut allergy are related to the action of Immunoglobulin E (IgE) and other anaphylatoxins, which act to release histamine and other mediator substances from mast cells (degranulation). In addition to other effects, histamine induces vasodilation of arterioles and constriction of bronchioles in the lungs, also known as bronchospasm (constriction of the airways).

Symptoms can include the following:^[3]

• vomiting
• diarrhea
• urticaria (hives)
• angioedema (swelling of the lips, face, throat and skin)
• acute abdominal pain
• exacerbation of atopic eczema
• asthma
• anaphylactic shock

The British Dietetic Association warns that: "If untreated, anaphylactic shock can result in death due to obstruction of the upper or lower airway (bronchospasm) or hypotension and heart failure. This happens within minutes to hours of eating the peanuts. The first symptoms may include sneezing and a tingling sensation on the lips, tongue and throat followed by pallor, feeling unwell, warm and light headed. Severe reactions may return after an apparent resolution of 1–6 hours. Asthmatics with peanut sensitivity are more likely to develop life threatening reactions."^[3]

[edit] Causes

The exact cause of someone developing a peanut allergy is unknown. Peanut allergy is more likely to develop in children who have 1st-degree relatives with atopic disease (allergies), and thus it probably shares genetic risk factors with other atopic diseases.^[4] A 2003 study found no link to maternal exposure to peanuts during pregnancy or during breast-feeding,^[5] though the data shows a linkage to the amount of time a child is breastfed. The same study indicated that exposure to soy milk or soy products was correlated with peanut allergies. However, an analysis of a larger group in Australia found no linkage to consumption of soy milk, and that the appearance of linkage is likely due to preference to using soy milk among families with known milk allergies.^[6][7] It's possible that exposure to peanut oils in lotions may be implicated with development of the allergy.^{[citation needed]} Another hypothesis for the increase in peanut allergies (and other immune and auto-immune disorders) in recent decades is the Hygiene hypothesis.

Comparative studies have found that delaying introduction of peanut products significantly increases the risks of development of peanut allergies,^[8][9] and the American Association of Pediatrics, in response to ongoing studies that showed no reduction in risk of atopic disease, rescinded their recommendation to delay exposure to peanuts along with other foods. They also found no reason to avoid peanuts during pregnancy or while breastfeeding.^[10] Pediatric Associations in Britain and Australia recommend delaying introduction until age 3 and have not changed their recommendations as of March 2009.^{[citation needed]}

[edit] Prevalence

The Asthma and Allergy Foundation of America estimates that peanut allergy is the most common cause of food-related death.^[11] However, deaths from food allergies are relatively rare, with an estimated one death per 830,000 children with food allergy each year, leading at least one authority to conclude that the danger has been greatly exaggerated via media sensationalism.^[12] Prevalence among adults and children is similar — around 1% — but at least one study shows it to be on the rise in children in the United States.^[13] The number of young children affected doubled between 1997 and 2002.^[14] 25% of children with a peanut allergy outgrow it.^[15] About 100 people per year die from peanut allergies.^[16]

One study has shown that peanut allergies are also dependent on race, in particular, Native Americans are less prone to be allergic to peanuts.^[17]

[edit] Treatments

See Anaphylaxis for the emergency treatment of an acute allergic reaction.

Currently there is no treatment to prevent or cure allergic reactions to peanuts.^[14] Strict avoidance of peanuts is the only way to avoid an allergic reaction. Children and adults are advised to carry epinephrine injectors to treat anaphylaxis.

While several companies have developed promising drugs to counteract peanut allergies, trials have been mired in legal battles.^[18]

[edit] Oral desensitization

A desensitization study at Duke University was done with escalating doses of peanut protein. Eight children with known peanut allergy were given escalating doses of peanut protein in the form of a flour mixed into applesauce or other food. The treatment included three phases: one day in the medical center, with increasing doses given throughout the day; a home phase lasting three or four months that involved daily, escalating doses; and a home maintenance phase in which the daily dose was 300 milligrams, about the equivalent of one peanut. The maintenance phase lasted up to 18 months, depending on how much peanut protein the child tolerated. Seven children completed the study. These children were given a "food challenge" to peanut flour, exposing them to up to nearly 8 grams, or the equivalent of more than 13 peanuts. Five of the seven children tolerated the equivalent of 13 peanuts at the food challenge at the end of the study.^[19] In February 2009 a successful desensitization study was announced by Addenbrookes Hospital in Cambridge, England.^[20]

[edit] Allergen-free peanuts

On July 20, 2007, the North Carolina Agricultural and Technical State University announced that one of its scientists, Dr. Mohamed Ahmedna, had developed a process to make allergen-free peanuts. Initial testing showed a 100 percent deactivation of peanut allergens in whole roasted kernels, and human serums from severely allergic individuals showed no reaction when exposed to the processed peanuts. Food companies have expressed an interest in licensing the process, which purportedly does not degrade the taste or quality of treated peanuts, and even results in easier processing to use as an ingredient in food products.^[21]

[edit] See also

• Christina Desforges, whose death from smoke-induced asthma was initially reported as an allergic reaction to peanut butter eaten by her boyfriend

[edit] References

[edit] External links

• "Are Nut Bans Promoting Hysteria?" by Tana Parker-Pope at The New York Times (15 Dec 2008)

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