Cherries, a type of stone fruit from the Rosaceae family, can cause allergic reactions. A food allergy occurs when the immune system mistakenly identifies specific proteins in the fruit as harmful invaders. This triggers an overactive response that can range in severity. Although cherries are not among the most common food allergens, their proteins can cause reactions in sensitized individuals.
Identifying the Symptoms of a Cherry Allergy
Reactions to cherries often begin almost immediately after consumption, starting with mild, localized symptoms. Individuals frequently notice an itching or tingling sensation affecting the mouth, tongue, and throat. This initial response may also involve slight swelling of the lips or face, known as angioedema. Skin reactions are also common, presenting as hives (raised, itchy welts) or generalized redness across the body.
The reaction can extend beyond the mouth and skin, affecting the digestive and respiratory systems. Gastrointestinal distress may include nausea, vomiting, abdominal pain, or diarrhea. More concerning symptoms involve the respiratory tract, such as wheezing, coughing, or difficulty breathing, signaling a potentially severe reaction.
In the most severe cases, a cherry allergy can trigger anaphylaxis, a life-threatening systemic reaction requiring immediate medical attention. Anaphylaxis involves multiple body systems simultaneously. It can cause a dangerous drop in blood pressure, a rapid heart rate, and severe airway constriction. Recognizing signs of an escalating reaction, particularly difficulty breathing or feeling faint, is crucial for timely intervention.
The Specific Proteins That Cause Reactions
The allergic reaction is an immune response directed at specific protein components within the cherry fruit. Scientists have identified several proteins in sweet cherries (Prunus avium) that act as allergens, including Pru av 1, Pru av 2, Pru av 3, and Pru av 4. The immune system of an allergic person produces specialized Immunoglobulin E (IgE) antibodies that bind to these proteins. When a sensitized individual consumes a cherry, the IgE antibodies attach to the protein, initiating the release of inflammatory chemicals like histamine.
The most frequently studied cherry allergen is Pru av 1, a PR-10 protein. This protein often causes milder, localized reactions because heat and digestive enzymes easily break it down. Other proteins, such as Pru av 3, a Lipid Transfer Protein (LTP), are more stable and resist both heat and digestion. Due to this stability, reactions involving Pru av 3 are more likely to cause systemic and severe symptoms.
Cross-Reactivity and Pollen Food Syndrome
The most common reason for a cherry allergy in adults is Pollen Food Syndrome (PFS), previously known as Oral Allergy Syndrome (OAS). This condition results from cross-reactivity, where the immune system confuses cherry proteins with similar proteins found in inhaled allergens. Cherries belong to the Rosaceae family, and their proteins share structural similarities with Bet v 1, the major allergen in birch pollen.
Individuals primarily allergic to birch pollen may develop IgE antibodies that recognize the similar Pru av 1 protein in cherries. When these antibodies encounter the cherry protein, they trigger an allergic response, typically confined to the mouth and throat. This cross-reaction means that up to 70% of people with a birch pollen allergy may experience PFS symptoms when eating stone fruits.
The allergic proteins involved in PFS, such as Pru av 1, are heat-labile, meaning cooking or processing easily destroys them. Therefore, many individuals with a cherry allergy due to PFS can safely consume cooked cherry products, such as pie filling or jam. However, the proteins responsible for more severe, systemic reactions are more stable and may still cause symptoms even after heating.
Seeking Diagnosis and Managing Avoidance
Anyone who suspects a cherry allergy should consult an allergist for proper testing and diagnosis. The allergist will begin with a detailed medical history, followed by diagnostic tests to confirm the presence of IgE antibodies. A common method is the skin prick test, where a small amount of cherry extract is placed on the skin. A reaction, such as a raised bump, indicates sensitization.
Blood tests are also used to measure specific IgE antibodies against cherry proteins. This helps differentiate between a milder PFS and a more systemic allergy. In some cases, a carefully monitored oral food challenge may be conducted under medical supervision to confirm the diagnosis. Diagnosis is followed by a management plan focused on strict avoidance of the allergenic food.
Management involves strictly avoiding fresh cherries and any products containing them, requiring careful label reading of baked goods, juices, and liqueurs. For individuals prone to mild reactions, an allergist may recommend over-the-counter antihistamines. Those at risk for severe reactions are prescribed an epinephrine auto-injector, which should be carried at all times for emergency use.