A food allergy represents an overreaction by the body’s immune system to a protein that is normally harmless. The immune system mistakenly identifies this protein as a threat, triggering a defensive response. It is entirely possible to develop an allergy to cherries or any food suddenly, even if it has been consumed many times before without reaction. This phenomenon is often referred to as “adult-onset allergy” and accounts for a significant number of new food allergy diagnoses each year.
The Mechanism of Sudden Allergic Sensitization
The process of becoming allergic involves two distinct phases: sensitization and reaction. During sensitization, the body produces Immunoglobulin E (IgE) antibodies after encountering the cherry protein. These IgE antibodies attach to the surface of immune cells, primarily mast cells, located throughout the body’s tissues. This initial phase occurs without noticeable symptoms, which is why the allergy appears to begin suddenly.
The specific allergenic proteins in sweet cherries (Prunus avium) include Pru av 1, Pru av 2, Pru av 3, and Pru av 4. These proteins are recognized by the pre-formed IgE antibodies. When a person eats cherries again after being sensitized, the cherry proteins cross-link the IgE on the mast cells, acting like a trigger. This cross-linking signals the mast cells to release potent chemical mediators, such as histamine, causing the rapid onset of allergic symptoms.
The Connection to Pollen: Oral Allergy Syndrome
The most common reason for a sudden, adult-onset cherry allergy is Oral Allergy Syndrome (OAS), also known as Pollen Food Allergy Syndrome (PFAS). This syndrome involves molecular mimicry, where the immune system confuses cherry proteins with similar proteins found in environmental pollens. For cherry allergy, the primary link is often to birch pollen, which contains the protein Bet v 1.
The immune system, already sensitized to Bet v 1, mistakes the structurally similar cherry protein, Pru av 1, for the pollen allergen. Because the cherry protein is quickly degraded by enzymes in the saliva and stomach, the reaction typically remains localized. This protein breakdown prevents the allergen from entering the bloodstream in large amounts and triggering a systemic response. Consequently, symptoms are usually confined to areas of contact, such as the mouth and throat.
Reactions caused by OAS are typically milder than those caused by other food allergies, though severity varies. The cross-reactive proteins responsible for this milder form are often sensitive to heat. This means a person may be able to eat cooked cherries, such as those in a pie or jam, without issue. This heat sensitivity is a distinguishing feature of OAS compared to more severe, systemic allergies.
Identifying Symptoms and Severity Levels
Cherry allergy symptoms range from localized discomfort to life-threatening emergencies. Mild, localized reactions are characteristic of Oral Allergy Syndrome and typically begin immediately after eating the fruit. These symptoms include an itchy or tingling sensation in the mouth, lips, or throat, and sometimes minor swelling of the lips or tongue.
The reaction can escalate to involve other parts of the body, indicating a more systemic allergy. Skin reactions may include hives (raised, itchy welts) or generalized itching. Gastrointestinal symptoms, such as nausea, vomiting, or abdominal pain, may also occur as the body attempts to expel the perceived threat.
The most severe form of allergic reaction is anaphylaxis, which requires immediate emergency medical care. Signs of anaphylaxis include difficulty breathing due to throat swelling or wheezing, a rapid or weak pulse, and dizziness or fainting caused by a sudden drop in blood pressure. Recognizing these severe signs is important, as anaphylaxis can progress quickly and be fatal without prompt treatment.
Diagnosis and Long-Term Management
If a new reaction to cherries is suspected, the first step is to consult an allergy specialist for a precise diagnosis. The diagnostic process often begins with a skin prick test, where small amounts of cherry extract are placed on the skin to check for a localized reaction. A blood test to measure the level of cherry-specific IgE antibodies in the bloodstream is also commonly performed.
Identifying the specific allergenic protein, such as Pru av 1 or Pru av 3, helps the allergist understand the nature of the allergy, such as whether it is OAS-related or systemic. In certain controlled circumstances, an oral food challenge may be necessary to confirm the diagnosis. This involves consuming small, increasing amounts of the cherry under direct medical supervision.
The most effective long-term management strategy is the strict avoidance of raw cherries and products containing them. Reading ingredient labels carefully is necessary, looking for the scientific name, Prunus avium, or any cherry derivative. For individuals who have experienced systemic or severe reactions, carrying an epinephrine auto-injector is a necessary precaution. This device delivers a dose of epinephrine that quickly counteracts the effects of anaphylaxis while waiting for emergency services to arrive.