Oral mite anaphylaxis

Overview

Oral Mite Anaphylaxis (OMA), also known as "Pancake Syndrome," is a rare but potentially life-threatening allergic reaction that occurs after the ingestion of foods contaminated with mites. The condition was first described in tropical and subtropical regions, where storage mites are more prevalent due to warm and humid climates. OMA typically presents within minutes to a few hours after eating flour-based foods like pancakes, biscuits, or cakes that have been made with mite-contaminated flour.

This syndrome is particularly concerning because the contaminated food may appear normal to the naked eye, and the exposure is often unsuspected. It most frequently affects individuals with a history of asthma, allergic rhinitis, or sensitivity to house dust mites. Prompt recognition and emergency treatment are critical to prevent severe anaphylactic reactions.

Causes

Oral Mite Anaphylaxis is triggered by the ingestion of food contaminated with mites, particularly storage mites. These mites can proliferate in improperly stored flour or grain-based products.

Common Mite Species Involved

• Dermatophagoides farinae and Dermatophagoides pteronyssinus (house dust mites)

• Blomia tropicalis (common in tropical climates)

• Lepidoglyphus destructor and Tyrophagus putrescentiae (storage mites)

Risk Factors

• Use of long-stored flour: Especially when stored at room temperature in humid environments.

• History of mite allergy: Patients already sensitized to dust or storage mites.

• Pre-existing allergic conditions: Asthma, allergic rhinitis, or atopic dermatitis increase susceptibility.

• Lack of refrigeration: Storing flour outside the refrigerator encourages mite growth.

Symptoms

Symptoms of Oral Mite Anaphylaxis typically appear shortly after ingestion of contaminated food and resemble those of classical food-induced anaphylaxis.

Early Symptoms

• Itching or tingling in the mouth and throat

• Facial or lip swelling (angioedema)

• Hives (urticaria)

• Nasal congestion or sneezing

Severe Symptoms (Anaphylaxis)

• Wheezing and shortness of breath

• Bronchospasm and chest tightness

• Drop in blood pressure (hypotension)

• Rapid pulse and dizziness

• Loss of consciousness

In some patients, especially those with asthma, respiratory symptoms can be especially severe and require urgent medical intervention.

Diagnosis

Diagnosis of Oral Mite Anaphylaxis involves a thorough clinical history, allergen testing, and sometimes analysis of the suspected food source.

Clinical Evaluation

• History of reaction: Temporal relationship between ingestion of flour-based food and allergic symptoms.

• Recurrent episodes: Especially with certain home-cooked meals using long-stored flour.

Allergy Testing

• Skin prick testing: Using mite extracts to test for sensitization to house dust or storage mites.

• Specific IgE blood tests: To confirm sensitization to mite allergens.

Food Sample Analysis

• Microscopic examination of the flour or food consumed can reveal the presence of live or dead mites.

Differential Diagnosis

• Classical food allergy (e.g., egg, milk, peanut)

• Exercise-induced anaphylaxis

• Other contaminant-induced reactions (e.g., mold or bacterial toxins)

Treatment

Treatment of Oral Mite Anaphylaxis follows the general principles of anaphylaxis management and includes both emergency response and long-term prevention strategies.

Emergency Management

• Epinephrine: Intramuscular injection is the first-line treatment for anaphylaxis.

• Antihistamines: To relieve hives and itching.

• Corticosteroids: May help prevent recurrence or biphasic reactions.

• Oxygen and bronchodilators: For patients with respiratory distress or asthma.

• Hospitalization: In moderate to severe cases for observation and supportive care.

Preventive Strategies

• Refrigerate flour and grains: Store flour in sealed containers in the refrigerator or freezer.

• Use fresh flour: Discard old or suspect flour, especially if stored in humid environments.

• Label awareness: Educate patients with mite allergy about avoiding high-risk foods.

• Allergen immunotherapy: May be considered for long-term control of dust mite allergy in sensitized individuals.

Prognosis

With prompt recognition and treatment, the immediate prognosis for Oral Mite Anaphylaxis is generally good. However, recurrence is possible if exposure to contaminated food continues. Patients with asthma are at higher risk of severe respiratory complications.

By implementing preventive measures, including safe food storage practices and mite avoidance strategies, patients can significantly reduce their risk of future reactions. Education about anaphylaxis management, including carrying epinephrine auto-injectors, is essential for long-term safety.