A cherry allergy, a reaction to Prunus avium (sweet cherry), can range significantly in severity from mild discomfort to a life-threatening emergency. While less frequently discussed than allergies to peanuts or shellfish, the immune system mistakenly identifies specific cherry proteins as a threat. This reaction is often linked to existing sensitivities, but it can also manifest as a standalone food allergy.
Understanding the Cause of Cherry Allergies
Cherry allergy is typically categorized into two main types based on the specific protein involved. The most common is Pollen Food Allergy Syndrome (PFAS), a cross-reaction phenomenon. PFAS occurs when the immune system confuses cherry proteins with similar proteins found in certain tree pollens, particularly birch pollen. The primary allergen responsible for this cross-reactivity in cherries is Pru av 1, which belongs to the pathogenesis-related protein family 10 (PR-10).
The structure of Pru av 1 closely resembles Bet v 1, the major allergen in birch pollen. This type of reaction is generally localized and mild because Pru av 1 is highly sensitive to heat and digestion. Once the protein is broken down by cooking or stomach acid, it loses its ability to trigger a reaction. This is why many individuals with PFAS can tolerate cooked cherries.
A less common, but more severe, form of cherry allergy is a primary allergy unrelated to pollen sensitivity. This systemic reaction is caused by a different protein called Pru av 3, a non-specific Lipid Transfer Protein (LTP). Unlike Pru av 1, LTPs are highly resistant to heat, enzymes, and digestion. Because they survive the digestive process, they can travel beyond the mouth and throat to cause widespread reactions.
LTP-related cherry allergy is more prevalent in Mediterranean regions, where sensitization to related proteins in peach (Pru p 3) is common. Individuals with an LTP allergy often react to cherries in all forms, including processed products like jams and juices. This primary allergy can trigger a widespread systemic response.
Recognizing Allergic Reactions
Allergic reactions vary depending on the underlying protein involved, with mild reactions being the most frequent presentation. Reactions stemming from PFAS are usually confined to the area of contact. Symptoms typically begin almost immediately after consuming raw cherries and may include a tingling, itching, or scratchy sensation inside the mouth, on the lips, or in the throat. Localized symptoms, such as slight swelling of the lips, tongue, or palate, often resolve quickly once the fruit is swallowed or removed.
In contrast, an allergy mediated by the heat-stable LTPs can trigger systemic symptoms that extend throughout the body. Skin reactions may include the sudden appearance of hives or generalized itching. Digestive distress is also common, involving nausea, vomiting, abdominal pain, or diarrhea. These gastrointestinal symptoms usually manifest within one to two hours of ingestion.
The most severe reaction is anaphylaxis, which involves multiple body systems and requires immediate emergency medical care. Signs of anaphylaxis include respiratory issues such as wheezing, coughing, or shortness of breath. Cardiovascular symptoms, such as dizziness, a rapid or weak pulse, or low blood pressure, also signal an anaphylactic event. Prompt recognition and action are necessary if anaphylaxis is suspected.
Testing and Treatment Options
Diagnosis of a cherry allergy begins with a detailed review of the patient’s medical history by an allergist. Standard diagnostic tools include the skin prick test (SPT), where a small amount of cherry extract is applied to the skin to check for a localized reaction like a raised bump or wheal. Blood tests are also utilized to measure the level of Immunoglobulin E (IgE) antibodies specific to cherry proteins.
Specific IgE testing identifies which allergen component, such as Pru av 1 or Pru av 3, is causing the reaction. This helps predict the severity of the allergy and determine which forms of cherry may be safe to consume. In some instances, an allergist may recommend an oral food challenge, which must be performed in a medical setting with emergency resources available.
Management requires strict avoidance of the fruit and any products containing it. For individuals with a Pru av 1-related allergy (PFAS), cooking or heating cherries often denatures the allergenic protein, making cooked products tolerable. However, this heat treatment is ineffective for those sensitized to the Pru av 3 (LTP) protein, who must avoid all forms of cherry.
For mild, localized symptoms, over-the-counter antihistamines can alleviate discomfort. For those at risk for systemic reactions, emergency preparedness is paramount. The allergist will prescribe an epinephrine auto-injector, which must be administered immediately at the first sign of a severe reaction. Patients and their families should be educated on recognizing anaphylaxis symptoms and correctly using the auto-injector.