Are flax seeds and sesame seeds related to Oral Allergy Syndrome (OAS)?

Flax Seeds and Sesame Seeds in Oral Allergy Syndrome

Flax seeds and sesame seeds can both trigger allergic reactions but are not typically associated with classical oral allergy syndrome (OAS), which is primarily related to pollen-food cross-reactivity.

Understanding Oral Allergy Syndrome vs. Seed Allergies

Oral Allergy Syndrome (OAS) is characterized by:

• Immediate allergic reactions confined to the oral cavity after consuming fresh fruits and vegetables
• Cross-reactivity between pollen allergens and similar proteins in plant foods
• Symptoms typically include itching, tingling, and swelling of lips, mouth, and throat
• Usually milder than systemic food allergies 1

Seed allergies, including flax and sesame, differ from OAS in important ways:

• They represent true food allergies rather than cross-reactions with pollens
• Reactions can be systemic and severe, not just limited to the oral cavity
• The allergens involved are primarily seed storage proteins (2S albumins and 11S globulins)
• These allergies are not typically seasonal or related to pollen exposure 2

Flaxseed Allergy

Flaxseed allergies have been increasingly reported as consumption has grown:

• Severe systemic reactions can occur after flaxseed consumption
• Key allergens identified include:
  • 2S albumin (Lin u 1) - recognized in the WHO/IUIS allergen nomenclature
  • 11S globulin - recently identified as a potential allergen
• Cross-reactivity has been demonstrated between flaxseed 2S albumin and proteins in peanuts and cashew nuts 3
• Reactions are typically IgE-mediated true food allergies rather than OAS

Sesame Seed Allergy

Sesame seed allergy is more prevalent and better documented:

• Estimated prevalence of 0.1-0.2% of the population
• Now recognized as the 9th major food allergen in the US requiring mandatory labeling
• Sesame seed oil can also trigger allergic reactions, unlike most refined oils
• Reactions can be severe and potentially life-threatening 2, 4
• The allergenicity of sesame oil varies based on processing methods, with cold-pressed oils retaining more allergenic proteins 5

Diagnostic Considerations

For suspected seed allergies:

• Skin prick tests with commercial extracts may have poor sensitivity for seed allergies
• Fresh seed extracts provide better diagnostic accuracy for skin testing
• Specific IgE testing may have mediocre sensitivity for sesame and other seeds
• Oral food challenges remain the gold standard for diagnosis 2, 4
• Double-blind placebo-controlled food challenges are recommended when the history is unclear 5

Management Approach

For patients with confirmed seed allergies:

1. Complete avoidance of the offending seed and products containing it
2. Education about hidden sources of seeds in processed foods
3. Emergency preparedness with appropriate medications, including epinephrine auto-injectors for those with history of severe reactions
4. Careful label reading, noting that while sesame is now required on US food labels, flaxseed is not 6
5. Consider cross-reactivity with other seeds and nuts when developing avoidance strategies

Important Distinctions

It's crucial to distinguish between:

• True seed allergies (potentially severe, systemic reactions)
• Oral Allergy Syndrome (typically milder, oral cavity symptoms)
• Food intolerances (non-immunologic adverse reactions) 5

This distinction impacts management decisions, particularly regarding the need for emergency medications and the strictness of avoidance measures.

Clinical Pearls

• The prevalence of seed allergies appears to be increasing with greater incorporation of seeds in various food products
• Sesame can be a "hidden allergen" in many foods, including bakery products, tahini, hummus, and certain medications
• Flaxseed is increasingly used in health foods, supplements, and baked goods
• Both seeds can cause severe reactions in sensitized individuals, unlike typical OAS which rarely causes systemic reactions