Peanut Allergy Primer

by Dr. Keith I. Lenchner
May 08, 2012

August 2011, a 15-year-old boy from Lawrenceville, Georgia took a bite of a cookie, unaware that it contained peanuts. Within seconds his throat began to swell. Despite a history of peanut allergy, he had forgotten to carry his rescue medicine (epinephrine) with him when he left home that morning. He ran to a nearby restaurant to wash the cookie from his mouth, but it was too late. Minutes later he died.

Fortunately, incidents like this are rare, but in 2007 an estimated 3 million U.S. children under 18 years of age had a reported food allergy and 150–200 children died as a result. “Although any child can be at risk for food allergies, children are at greater risk if they are younger than age 3 or have a family history of asthma and allergies, a genetic predisposition to allergic disease, or elevated allergen-specific serum immunoglobulin levels (IgE concentrations),” says the Centers for Disease Control and Prevention (CDC). Eight foods account for 90 percent of all food allergies—cow’s milk, eggs, peanuts, tree nuts, fish, shellfish, soybeans, and wheat. Peanut is among the most common food allergens, along with milk and shellfish.

What is peanut allergy?
Peanut allergy, like most allergies, is an over-reaction of the immune system to a protein that would otherwise be harmless. When individuals with peanut allergy are exposed to peanut protein through ingestion, skin contact, or inhalation, they make allergic antibodies known as immune globulin E (IgE).  These antibodies attach to the surface of cells in the nose, eyes, skin, throat, stomach, and lungs. Peanut protein binds to the IgE antibodies, which in turn release histamine and other chemicals into the surrounding tissues causing allergic symptoms such as runny nose, watery eyes, itching, sneezing, wheezing, swelling of the throat and tongue, and hives.

How does my child get peanut allergy?
It’s unclear why some children develop peanut allergies but genetics play a role. Children whose parents or siblings have food allergy may be at greater risk for developing peanut allergy and may be tested prior to eating peanut products. The allergy community previously recommended that children at high risk for food allergy avoid cow’s milk for the first year of life, egg for the first two years, and peanuts, tree nuts, fish, and shellfish for the first three years. However, there is no strong evidence that these recommendations successfully prevent food allergy in these high-risk children. As a result, in 2008, the American Academy of Pediatrics (AAP) revised its recommendations. “We just do not have the studies to back this up. If a child is going to be allergic to peanuts or eggs, it doesn’t seem to matter [after 4 to 6 months] when you introduce these foods,” says study co-author Frank Greer, MD.

Similarly, the American Academy of Allergy, Asthma, and Immunology does not recommend that breastfeeding mothers (even those with a family history or allergy) change their diets in an effort to reduce their babies’ risk of food allergy. Although not fully understood, several recently published studies imply that earlier exposure to common food allergens (around 6 months) may actually help prevent food allergy in newborns.

What are the signs/symptoms of food allergy?
Food allergic individuals typically experience stomach upset or nausea within 30 minutes to two hours after ingestion. Hives or red, itchy welts are probably the second most common symptom to develop but may occur along with:

• difficulty breathing and wheezing
• red, itchy eyes
• swelling of the hands and face
• difficulty swallowing
• hoarseness
• light-headedness

Small children might grab their tongue or make comments like “there’s a bug in my throat” to communicate their symptoms. In more severe cases, children may experience a loss of consciousness and even death, a rare but devastating occurrence. If symptoms begin more than two hours after ingestion, food allergy becomes less likely. Most food allergy symptoms resolve within 24–36 hours.

What is the treatment?
Peanut avoidance is currently the recommended treatment for patients with peanut allergy. Several academic centers are successfully desensitizing children with peanut and other food allergies but this process involves a high risk of allergic reaction and is not recommended as a routine treatment. In these special centers, children and adults with food allergy are fed their culprit food in gradually increasing amounts until they can tolerate significant portions. Patients continue to eat the food on a daily basis to ensure that an accidental ingestion will not result in allergic symptoms. It’s not known how long an individual may have to continue to eat the culprit food before they actually become tolerant and lose their allergy.

How is peanut allergy diagnosed?
If you want to know more definitively whether your child may be allergic to peanut or other food allergens, skin or blood testing by a pediatrician or a board certified allergist is advised. Unfortunately, both of these tests are plagued by a high false positive rate (up to 50 percent!). However, these tests are quite sensitive, which means that a negative result rules out food allergy with better certainty.

A food challenge (having the child eat a small amount of the culprit food) is the gold-standard method for diagnosing food allergy. However, it presents significant risk for an allergic reaction, therefore it should be conducted by a board certified allergist. Up to 20 percent of patients with peanut allergy will outgrow the allergy, but the real challenge is to determine at what age. Skin or blood tests every 1–2 years may help patients and their allergists figure out when would be a safe time conduct a food challenge.

How can peanut allergy be prevented?
Most allergists advise peanut allergic children to avoid all nuts, including tree nuts such as almonds, pecans, walnuts, etc. Peanuts are actually part of the legume family but approximately 35 percent of peanut-allergic patients may also be allergic to tree nuts.  Parents often find a policy of total nut avoidance easier to follow for their peanut allergic children, especially given the chances for cross-contamination in cafeterias, restaurants, or factories. Breastfeeding mothers with peanut-allergic infants must avoid peanut protein themselves to avoid transfer via their breast milk, as well as oral to oral transfer. (Transfer of peanut protein can occur when a mother eats peanut products and then kisses her baby.)