More than 3 million people in the United States report being allergic to peanut, tree nuts, or both. Since 1997, the percentage of children with peanut allergy has more than doubled in the United States.
Approximately 60% of fatal food anaphylaxis is caused by peanuts.
What is a peanut?
The botanical name for a peanut plant is Arachis hypogea. It is a member of the legume family (soy, peas, beans).
Each peanut kernel (usually 2 per shell) contains about 325 milligrams of peanut protein along with sugar and fats. The peanut protein is what causes allergic reactions.
The fat does not cause allergic reactions (Peanut oil is made of fat, small amounts of peanut protein may contaminate the fat.)
Three of the peanut proteins, Ara h1, Ara h2, and Ara h3 have been most closely linked to serious peanut allergic reactions.
Oral Allergy Syndrome
Ara h8 is similar to a protein found in birch tree pollen. If a patient is allergic to only Ara h8 severe reactions are rare (but do occur).
Most patients have only mild itching/burning of the mouth, tongue, lips and/or throat.
Peanut allergy testing, whether it is done by skin testing or blood testing will be positive regardless of which specific peanut protein the person is allergic to. Component testing is available to identify which specific peanut proteins are causing the problems.
With all allergies, for each allergic person, there is an amount of protein above which an allergic reaction occurs and below which nothing noticeable happens.
For adults and children, it has been shown some patients react to as little as 0.1mg of peanut protein, others required 3,000mg (9 peanut kernels) to react.
A person’s threshold can change (increase or decrease), either on its own with time, during viral illnesses (decrease), menstruation (decrease), exercise(decrease), or with oral immunotherapy(increase).
Who becomes peanut allergic?
In families with a tendency for allergies several studies suggest that the mother’s avoidance of peanut in pregnancy/breastfeeding does not reduce the chance of an infant becoming peanut allergic.
There no current convincing evidence that delaying peanut introduction beyond 4-6 months of age has a significant protective effect.
There is some evidence that delaying the introduction of peanuts may have played a role in the increasing incidence of peanut allergy.
Past reactions do they predict future reactions?
No! Patients with mild reactions in the past can have a severe life threatening reaction, and patients with known severe reactions can have a mild reaction.
It is not true that reactions get worse with each exposure.
Does the score for peanut skin testing or allergy blood testing predict the severity of reactions?
No, severe reactions can occur whether the positive score is high or low. On rare occasions reactions can occur even when the tests are negative.
High skin test and/or allergy blood test scores, are not a guarantee that an allergic reaction will occur.
Using the Test Scores
For patients who regularly eat peanut products with out reactions, having a positive peanut allergy skin test or blood test rarely suggests future peanut problems and peanut consumption should be continued.
The positive predictive value of peanut blood testing is 100% with specific peanut IgE >14 KU/L. This means if your level is above 14 you have a 100% chance of reacting if peanut protein enters your body.
The odor of peanuts is due to an organic volatile compound called pyrazine, which contains no peanut proteins and, therefore, does not cause allergic reactions.
There are situations where peanut protein could become airborne. Restaurants that offer customers peanuts in the shell could theoretically have peanut protein in their airborne dust as peanuts drop to the floor and becomes crushed.
Within an airplane, as passengers simultaneously open multiple packets of peanuts, peanut dust within the bags could become airborne. Allergic reactions under these circumstances are rare.
July 2008 study from the University of California’s Davis School of Medicine looked at allergic reactions aboard airliners among 471 people with severe peanut, nut or seed allergies. Forty-five of these passengers – almost 10 per cent – reported having reactions while in the air, with symptoms such as vomiting, wheezing, hoarseness, hives, diarrhea and light-headedness. Six people went to an emergency department after landing, including one following a flight diversion for medical attention. Most study participants treated themselves, and in only three cases of severe reactions were the airline crew even made aware of the medical situation in progress.
2009, a study from the University of Michigan and the Food Allergy & Anaphylaxis Network (FAAN) found that one in three people who had an allergic reaction to peanuts or tree nuts aboard an airplane suffered anaphylaxis, the most severe form of a reaction.
Direct peanut skin contact
Washing of their hands with “soap and water” and commercial “wipes” removed all traces of peanut, plain water and hand sanitizers do not.
With respect to table tops and desks, peanut contamination can be removed by “soap and water,” wipes,” Formula 409 type cleaners, and cleaners with bleach. Dishwashing liquid has been shown to be less effective. Reusable sponges and rags should not be used as they may trap the protein and spread it around.
Peanut protein in saliva
After eating peanuts, saliva continues to contain peanut protein for several hours. T
If a peanut allergic person shares utensils, straws, or kisses with someone who has eaten peanuts within the past several hours, reactions, sometimes very serious, can occur.
Brushing teeth or chewing gum helped peanut disappear more quickly in some, but not all people.
Nuts and seeds
Peanuts are in the legume family as are peas, beans, and soy.
Peanut allergic patients will test positive to other legumes approximately 35% of the time, but have trouble eating other legumes only about 5% of the time.
Approximately 25%-50% of peanut allergic patients will have allergic reactions to tree nuts(almonds, cashews, pistachio, hazelnut, Brazil nut, walnut, pecan).
Seeds, especially sesame, and occasionally poppy/sunflower can cause allergic reactions in peanut allergic patients.
A history of dual allergic reactions to peanuts and tree nuts is associated with a 10-fold higher risk of allergy to sesame seeds.
Coconut almost never cross reacts with peanut. Nutmeg (seeds of the tropical tree species Myristica fragrans) does not either.
Lupine, a bean used to enrich some breads, cookies and pasta, and becoming more common place in European foods, has been shown to cause allergic reactions in some peanut allergic patients.
Is it possible to outgrow peanut allergy?
Yes. Overall, approximately 20% of young children will become tolerant of peanut products by teen age years.
Labeling may contain peanut/ tree nut by the food industry is voluntary.
FALCPA laws mandate that if the product’s recipe contains peanut it must be listed clearly on the package, it is optional for a company to mention peanut using the phrases “made in a facility that processes” or “may contain” if peanut is not in the recipe, but is present in a different product made in the same facility.
Studies have shown that products that state "may contain", "produced in a shared facility", and "Produced on shared equipment", can contain enough protein to cause a reaction. The amount of protein contamination fluctuates dramatically and you can tolerate a food containing these statements many times before you eat the "loaded" food and have a reaction.
See Food Allergen Avoidance
How should peanut allergy be treated?
All people who have had an allergic reaction to peanut should carry or have immediately available injectable epinephrine.
Two doses of injectable epinephrine should be available. Up to 25% of peanut allergy attacks require a second dose. The second dose can be given within five minutes if symptoms are worsening or not showing improvement.
Once epinephrine has been injected “911” should be called. In the Emergency Room. Even with proper treatment , there should be at least 4 hours of Emergency Room observation to watch for return of anaphylaxis.
Anaphylactic reactions can return any where up to 24hrs after the initial reaction (bi-phasic reaction)