Quick Answer
Peanut allergy is the most common cause of food-related anaphylaxis and affects approximately 1.2–2% of the US population. It is caused by IgE antibodies to peanut proteins, especially Ara h 2. Symptoms range from skin hives to life-threatening anaphylaxis. Treatment includes strict avoidance, epinephrine auto-injectors, and optionally oral immunotherapy.
Peanut Allergens: What the Immune System Reacts To
Peanuts contain at least 17 identified allergen proteins, designated Ara h 1 through Ara h 17. The most clinically significant are Ara h 2 (a 2S albumin), which is the strongest predictor of systemic reactions and is detected in patients at highest risk for anaphylaxis; Ara h 1 and Ara h 3, which cause a range of reaction severities; and Ara h 8, a PR-10 protein that cross-reacts with birch pollen and typically causes only oral allergy syndrome.
Component-resolved diagnostics can test for specific Ara h proteins, allowing allergists to stratify reaction risk. High Ara h 2 sensitivity strongly predicts systemic anaphylaxis risk, while isolated Ara h 8 sensitivity typically indicates pollen-food allergy syndrome with only mild oral symptoms rather than systemic allergy.
Symptoms of Peanut Allergy
Peanut allergy symptoms span the full spectrum of IgE-mediated reactions: mild oral tingling or hives; moderate urticaria, vomiting, and rhinitis; and severe anaphylaxis with throat closure, bronchospasm, and cardiovascular collapse. Peanut allergy is responsible for approximately 150–200 food allergy deaths annually in the United States, making reaction severity recognition critical.
Reactions typically begin within 5–30 minutes of peanut ingestion. In highly sensitized individuals, even trace exposures from shared equipment, kissing a peanut-consumer, or airborne roasting peanut exposure can potentially trigger symptoms, though airborne reactions are considerably less common than ingestion reactions.
Early Peanut Introduction: The LEAP Trial
The landmark LEAP (Learning Early About Peanut Allergy) trial, published in 2015, demonstrated that introducing peanut products to high-risk infants (those with severe eczema or egg allergy) between 4 and 11 months of age reduced peanut allergy development by 80% compared to avoidance. This finding reversed 15 years of medical guidance advising delayed introduction.
Current NIAID guidelines (2017) recommend early peanut introduction at 4–6 months for high-risk infants, with allergist evaluation (and potentially supervised introduction) for those with severe eczema or established egg allergy, and routine early introduction for moderate- and low-risk infants. Age-appropriate peanut-containing foods (smooth peanut butter thinned with water, peanut puffs) are recommended from around 6 months.
Treatment: Avoidance, Epinephrine, and Oral Immunotherapy
Strict peanut avoidance remains the cornerstone of peanut allergy management. This includes reading all food labels (peanuts must be declared under FALCPA), alerting restaurants, carrying two epinephrine auto-injectors at all times, wearing medical identification, and having a written emergency action plan reviewed by an allergist.
Palforzia (AR101), the first FDA-approved peanut OIT product, is indicated for desensitization in patients ages 4–17. Treatment uses a structured up-dosing protocol over approximately 6 months to achieve a maintenance dose of 300mg peanut protein daily. Palforzia reduces the risk of severe reactions from accidental ingestion but does not eliminate peanut allergy and requires ongoing daily maintenance dosing.
Key Takeaways
- Peanut allergy affects 1.2–2% of Americans and is the leading cause of food allergy fatality.
- Ara h 2 is the most important peanut allergen component predicting systemic reaction risk.
- LEAP trial: early peanut introduction at 4–11 months reduces peanut allergy by 80% in high-risk infants.
- Every peanut-allergic patient needs two epinephrine auto-injectors and a written emergency action plan.
- Palforzia OIT can desensitize peanut-allergic patients but requires lifelong maintenance dosing.
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