A food allergy is an immune system response that occurs shortly after eating a specific food, where the body mistakenly identifies a protein in that food as a threat. The immune system then releases chemicals that cause allergic symptoms. Peach allergy, a reaction to the fruit Prunus persica, is a common type of food allergy, particularly in certain regions. The severity and nature of the reaction can vary widely, depending on the specific proteins within the peach that trigger the immune response.
Identifying the Reaction Symptoms and Severity
Symptoms often appear within minutes of consumption, presenting on a spectrum of severity. Mild, localized reactions involve the mouth and throat, characterized by tingling, itching, or swelling of the lips and tongue. These immediate symptoms are commonly referred to as Oral Allergy Syndrome (OAS).
More serious reactions are systemic, affecting multiple body systems, and requiring immediate medical attention. These include widespread skin involvement (hives or angioedema) or gastrointestinal symptoms like vomiting and abdominal pain. The most life-threatening reaction is anaphylaxis, which manifests as difficulty breathing, wheezing, or a sudden drop in blood pressure.
Understanding Cross Reactivity
The cause of a peach allergy is often tied to an existing sensitivity to airborne allergens through a process called cross-reactivity. In many cases, particularly in central and northern regions, the allergy results from the immune system confusing peach proteins with proteins found in tree pollen. This phenomenon is known as Pollen-Food Allergy Syndrome (PFAS).
Pollen-Related Allergy (Pru p 1)
This type of cross-reactivity involves the peach protein Pru p 1, a member of the PR-10 protein family. Pru p 1 shares a high structural similarity with the major birch pollen allergen, Bet v 1. When sensitized to birch pollen, the immune system produces IgE antibodies that react to both the pollen and the similarly structured peach protein. Because Pru p 1 is sensitive to heat and digestion, this form of allergy typically results only in localized OAS symptoms, and cooked peaches are often tolerated.
Other foods share similar proteins with Pru p 1, leading to potential cross-reactions that cause OAS symptoms. These foods include other members of the Rosaceae family, such as apples, pears, apricots, and cherries.
Systemic Allergy (Pru p 3)
A different peach protein, Pru p 3, causes a more severe and systemic type of peach allergy, often seen in southern regions. Pru p 3 is a Lipid Transfer Protein (LTP) that is resistant to heat and digestive enzymes. This resistance means it can cause severe reactions like anaphylaxis, even when the peach is cooked or processed.
Diagnosis and Management
Confirming a peach allergy requires consultation with an allergist to identify the sensitizing protein. Diagnosis often begins with skin prick tests, where peach extract is introduced into the skin to observe a localized reaction. Blood tests measure Immunoglobulin E (IgE) antibodies specific to allergens like Pru p 1 or Pru p 3. In complex cases, an oral food challenge may be used to confirm the diagnosis.
The most effective management strategy is the strict avoidance of the trigger food. Individuals must carefully read all food labels, as peach ingredients can be hidden in unexpected products. For those experiencing only mild OAS symptoms, antihistamines may provide relief. However, for individuals with a history of severe reactions, the immediate use of an epinephrine auto-injector is the required emergency treatment.