Drugs & MedicationsPreventive Medicine


My sister-in-law has a peanut allergy. I’ve been with her twice when she’s had reactions, and it was a scary situation! These episodes were both in restaurants, and even though she asked her server, he/she may not really know if there are nuts in the entree’. Nor do they always know if the food was prepared using peanut oils. She’s even gone so far as to ask the restaurant manager what ingredients were used in the preparation or serving of the food, and once even demanded the chef be queried. In a restaurant situation, she is at a real disadvantage because there is no label to tell what she will be eating.

The reason for her concern is because being allergic to peanuts can be very serious. Allergic reactions such as angioedema (swelling of her lips, tongue, throat, and face), and anaphylaxis (trouble swallowing, trouble breathing, rapid heart rate, vascular collapse, ie. shock, unconsciousness) can be life-threatening. She carries an adrenaline syringe (an Epi-Pen autoinjector) with her at all times in case an emergency situation occurs. And it has! I’ve seen her inject herself with epinephrine twice when her lips and face were beginning to swell. I don’t blame her for being cautious and vigilant, and reacting before serious problems develop.

Food allergies occur in both children (8%) and adults (2%-3%) and about 40% of those allergic children have multiple allergies. As can be seen by the decreasing percentage, many children don’t carry the same allergies into adulthood. Foods that commonly cause allergies are peanuts, shellfish, cow’s milk, tree nuts, eggs, fish, soy, and wheat, with peanut allergy leading the way. Cow’s milk allergy causes typical swelling of the lips, tongue, and throat (angioedema) and differs from lactose intolerance which is characterized by bloating, gas, diarrhea, and possibly abdominal pain. 

The symptoms caused by food allergies depend on whether Immunoglobulin-E (IgE) is involved in mediating the reaction or not. IgE-mediated (caused) allergies occur within seconds to minutes and are manifested by itching, swelling, and vascular collapse/shock, ie. anaphylaxis. Non-IgE-mediated reactions are delayed by hours to days and differ in character being more constitutional (like diarrhea, abdominal pain, eczema). The severity of the allergic reaction is determined by the amount of food ingested at the time. But my sister-in-law would react immediately at the very slightest exposure to nuts.

As mentioned above, there is a major difference between true food allergies and food intolerances. Intolerances are adverse reactions that don’t involve the immune system and thus are usually not life threatening. They are mostly self-reported and reproducible, ie. high fructose corn syrup intolerant people have diarrhea, or similar reaction, every time they eat something containing HFCS. 

Diagnosing food allergies, most often and most successfully, is done by an oral food challenge. In this test, the patient is given the suspected allergen to see if a reaction occurs. This is the preferred diagnostic method, but must be done under physician supervision. Other testing methods are skin prick testing, or scratch testing, and serum IgE tests. In scratch testing, the skin, usually the large surface area of the back, is scratched or pricked. Then, a drop of a

prepared allergen is applied to the open skin. If a raised, red “wheal,” or hive-like, reaction occurs, the patient is probably allergic to that allergen. Serum IgE tests, on the other hand, are better for patients at high risk for anaphylaxis because they don’t actually expose the patient to the allergen. Instead, in the lab, they test the patient’s serum against number of possible allergens. The preferred method is the oral food challenge which many patients are hesitant to do for fear of a severe, irreversible allergic reaction.

The best treatment for food allergies is avoidance of the offending food. If you’re allergic to peanuts and you avoid eating them, you won’t have a reaction. If one does unknowingly ingest an allergen, epinephrine (adrenalin) is the emergency drug of choice. It is administered via a device called an autoinjector. Marketed as EPI-PEN, it contains a pre-set, single dose of epinephrine. Food allergy patients are warned to keep an Epi-Pen with them at all times, and at the first sign of a reaction, jab it through their clothing into their thigh muscle. The autoinjector needle is hidden inside the device and releases when it is jabbed into the thigh. The needle pops up and “auto-injects” a therapeutic dose of epinephrine into the thigh muscle. This device can be a life saver. 

Antihistamines, glucocorticoids, and inhaled beta adrenergic agonists can be used but are not first-line emergency treatment. They can be used to blunt reactions or to reduce symptoms already present. They work much slower and are much less effective than epinephrine. There are, unfortunately, no medications that prevent allergic reactions to food. Desensitization therapy (immunotherapy, ie. allergy shots) will sometimes induce tolerance to a food allergen, but it has a high risk of adverse effects. 

In 2004, Congress passed the U.S. Food Allergen Labeling and Consumer Protection Act that requires food labels to list if any of nine major food allergens are present as ingredients in prepared foods. Those nine ingredients are milk, eggs, peanuts, tree nuts, soy, wheat, fish, shellfish, and sesame. This law protects allergic patients from accidentally ingesting an allergen they didn’t know was in what they were eating.

As I mentioned early on, many food allergies present in childhood do not persist into adulthood. Those are reactions to cow’s milk, eggs, soy, and wheat. Unfortunately, allergies to peanuts, tree nuts, and shellfish are likely to be life long, and must be dealt with seriously. I know of parents who are terrified of their children’s food allergies and are over-protective. I can understand that attitude. The last thing a parent would want is to give their child a food that caused a severe reaction. All we can do is be vigilant, check labels, ask questions, and never be without an EPI-PEN. 

Reference: Bright DM, Stegall HL, Slawson DC. Food Allergies: Diagnosis, Treatment, and Prevention. AM Fam Phys 2023 August;108(2):159-165.

ADDENDUM: American Family Physician reports that “early introduction of peanuts, wheat, cooked eggs, and cow’s milk between 4 and 6 months of age decreases the risk of developing food allergies.”

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