It seems hard to believe, but the United States Peanut Council estimates that the average American ingests about 11 pounds of peanut products each year; about 55% as peanut butter and the rest in sweets, baked goods, and table nuts. America ranks third in the world in peanut production, behind only China and India. Interestingly, even though the consumption of peanuts per capita is similar in the United States and China, the prevalence of peanut allergy is much higher in America.

How common is peanut allergy?

It is not surprising that with this high rate of consumption, the prevalence of peanut allergy has increased steadily over the past two decades, especially in the United States and other westernized countries. Medical research has reported that sensitization (positive skin prick test) to peanuts has increased by 55%, while allergic reactions increased by 95% over a 10 year period. Today peanuts are believed to be one of the leading causes of food allergic reactions in the United States and, together with tree nuts, are probably the leading cause of fatal and near fatal anaphylaxis induced by food.

Peanut allergy has been described as being “epidemic” in some countries. Recent surveys of the general population found the prevalence of peanut allergy to be 0.6% in the United States. Peanut is ubiquitous within the US food supply, and a study examining the efficacy of food allergen avoidance found that 80% of all infants had been exposed to peanut products by their first birthday and virtually 100% by their second birthday.

In more than 70% of children with peanut allergy, symptoms develop after the first known exposure. Since these reactions are mediated through the IgE antibody, a prior exposure or sensitization must have occurred. Possible routes of prior sensitization include exposure in-utero as a result of the ingestion of peanuts during pregnancy, or during breast-feeding. Such theories have resulted in recommendations that mothers of babies at high-risk for allergies avoid the ingestion of peanuts during pregnancy and while nursing. A high-risk baby would be one in whom both parents have allergies or the presence of allergies in one parent and a sibling. To date, there is no definitive proof that such recommendations are preventative.

What other foods might the peanut allergic individual be allergic to?

The peanut is a member of the legume family and is not considered to be a true nut. It is reassuring to note that most peanut allergic individuals can eat other members of the legume family safely. In those allergic to peanuts, concomitant allergy to beans such as soy, green beans, and peas is generally 5% or less. Lupine, a bean that is processed into flour, may have a higher incidence of cross-reactivity with peanuts than other beans. Clinically more important is the higher incidence of co-allergy to tree nuts in the peanut allergic individual. Between 25 -50% of peanut allergic patients will also be allergic to at least one tree nut, even though tree nuts are from a different botanical family. Care should therefore be taken as the sharing of allergens among the foods can be clinically relevant.

What is the treatment for peanut allergy?

If one has had a reaction to peanut (or the other tree nuts), he/she should consult an allergist for testing in order to identify or confirm the offending food allergen. Once identified, the allergist will discuss peanut avoidance and educate the patient on the treatment of an accidental ingestion of peanut allergen.  Peanut allergy resolves spontaneously in only approximately 20% of children by school age.

Currently the only effective treatment for peanut allergy is avoidance. There is promising research on the development of a drug to bind the peanut specific antibody and oral vaccines for peanut allergy, but clinical research trials are still in very early stages. There is also research ongoing which attempts to alter the allergenic proteins in the peanut to make them less allergenic.

Peanut is ubiquitous in our environment. Therefore, allergic individuals are faced with numerous hurdles in avoiding accidental ingestion of peanuts. This can result in very significant quality of life issues for both patients and their families. This is especially challenging during the school age years when children have greater exposures and less supervision.

Patients with a known allergy to peanuts should be prepared at all times to treat an allergic reaction. A written emergency plan outlining the treatment will include the immediate use of a quick acting antihistamine, and the injection of epinephrine using an auto-injector (EpiPen or Twinject) at the first sign of systemic involvement. Patients should be prepared to repeat the injection of epinephrine, if necessary. Any patient having systemic symptoms should call for emergency assistance and should be observed in an emergency facility. It is imperative that patients and their family members know how to recognize the symptoms of an allergic reaction and are prepared to react appropriately and immediately. Your allergist is prepared to help educate and demonstrate the proper response.

Peanut avoidance diet

The key to an allergy avoidance diet is to avoid all foods or products containing the food you are allergic to. In order to avoid foods that contain peanuts, it is important to read food labels carefully. But, as hard as one tries, inadvertent exposure can occur in a variety of circumstances. It can occur as the result of peanut contamination of equipment used in the manufacture of various foods, inadequate food labeling, contamination of foods during cooking in restaurants, and unanticipated exposure such as the inhalation of peanut dust on an airplane. Such inadvertent exposures result in an allergic reaction every three to five years in the average patient with peanut allergy.

Although most peanut allergic individuals instinctively avoid peanut oil, it can be safely consumed in most cases. Since it is the allergen present in the pulp of the peanut to which one reacts, the highly processed, i.e., acid-extracted, heat distilled peanut oil can be safely consumed by such individuals. On the other hand, cold-pressed or extruded peanut oils contain the allergenic protein and may induce an allergic reaction.

How to read a label for a peanut-free diet

Be sure to avoid foods that contain any of the following ingredients:

• cold pressed, expressed, or expelled peanut oil
• ground nuts
• mixed nuts
• Nu-Nuts® artificial nuts
• peanuts
• peanut butter
• peanut flour

Foods that may indicate the presence of peanut protein include

• African, Chinese, Thai, and other ethnic dishes
• baked goods
• candy
• cereals
• chili, spaghetti sauce
• chocolate (candy, candy bars)
• crackers
• egg rolls
• hydrolyzed plant protein
• hydrolyzed vegetable protein
• ice creams, frozen yogurts, tofutti
• marzipan
• nougat

A word of caution

Food manufacturers may occasionally change the ingredients in the product without warning. It is a good idea to always read the product label before using it. It is much easier to prevent a food-allergic reaction than to treat one.