Is it safe to administer antihistamines, such as diphenhydramine (Benadryl) or loratadine (Claritin), to a patient with Oral Allergy Syndrome (OAS) and a birch pollen allergy who experiences nausea from non-cross-reacting foods?

From the Research

Antihistamines can be safely administered to patients with Oral Allergy Syndrome (OAS) and birch pollen allergy who experience nausea from non-cross-reacting foods, but they may not effectively address the underlying issue. For symptomatic relief, second-generation antihistamines like loratadine (Claritin) 10mg daily or cetirizine (Zyrtec) 10mg daily are preferred over first-generation options like diphenhydramine (Benadryl) due to fewer sedative effects 1. However, it's essential to understand that nausea from non-cross-reactive foods is likely not mediated by the same allergic mechanisms that antihistamines target. OAS symptoms typically occur when proteins in certain raw fruits, vegetables, and nuts cross-react with birch pollen allergens, causing localized oral symptoms. If nausea occurs with foods not known to cross-react with birch pollen, other causes should be investigated, such as food intolerances, gastroesophageal reflux, or other gastrointestinal conditions. Some studies suggest that subcutaneous immunotherapy using birch pollen extract can be effective in reducing OAS symptoms in patients with pollen-food allergy syndrome 1. Additionally, research on the immune response to Mal d 1, a major apple allergen, has shown that oral exposure to this protein can affect the immune response in patients with birch pollen allergy 2. Patients should keep a food diary to identify triggers and consider consulting with an allergist for skin prick testing or other diagnostic measures to determine the exact cause of their symptoms. It is also worth noting that prevention of birch pollen-related food allergy by mucosal treatment with multi-allergen-chimers has shown promise in mouse models, and may be a potential future treatment strategy 3. In terms of specific treatment, the most recent and highest quality study suggests that subcutaneous immunotherapy with birch pollen extract can be an effective treatment for OAS symptoms in patients with pollen-food allergy syndrome 1. Key points to consider include:

• Antihistamines may not effectively address the underlying issue of nausea from non-cross-reacting foods
• Other causes of nausea should be investigated, such as food intolerances or gastrointestinal conditions
• Subcutaneous immunotherapy with birch pollen extract may be an effective treatment for OAS symptoms
• Patients should keep a food diary and consider consulting with an allergist for further diagnosis and treatment.