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.. 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, an emergency situation requiring immediate attention and treatment with epinephrine.

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:The British Dietetic Association. Peanut Allergy Information for Dietitians. 1999 http://www.bda.uk.com/Downloads/peanutallergy.pdf

• 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."

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. A 2003 study found no link to maternal exposure to peanuts during pregnancy or during breast-feeding, 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. It's possible that exposure to peanut oils in lotions may be implicated with development of the allergy.Fact: date=March 2009 Another hypothesis for the increase in peanut allergies (and other immune and auto-immune disorders) in recent decades is the Hygiene hypothesis.