What is the relationship between seafood allergy/high Immunoglobulin E (IgE) levels and autism?

Relationship Between Seafood Allergy/High IgE and Autism

There is no established relationship between seafood allergies or high IgE levels and autism spectrum disorders based on current medical evidence.

Understanding Seafood Allergies

Mechanism of Seafood Allergies

• Seafood allergies are among the most common food allergies worldwide, with shellfish allergy affecting up to 3% of the adult population and fish allergy affecting approximately 1% 1
• The primary allergen in shellfish is tropomyosin, a muscle protein that has been identified as the major allergen in oysters (Cra g 1), abalone (Hal m 1), and squid (Tod p 1) 2
• Tropomyosin has also been identified as an important allergen in other invertebrates including dust mites and cockroaches, leading some to propose it as an "invertebrate pan-allergen" 3
• IgE-mediated reactions to seafood typically cause immediate symptoms occurring within minutes to a few hours after ingestion 4

Prevalence of Seafood Allergies

• Seafood allergy prevalence rates in the United States are significantly lower for children than adults: fish allergy (0.2% for children vs. 0.5% for adults), crustacean shellfish allergy (0.5% vs. 2.5%), and any seafood allergy (0.6% vs. 2.8%) 4
• Women have higher prevalence rates than men for crustacean shellfish allergy (2.6% vs. 1.5%) and fish allergy (0.6% vs. 0.2%) 4

Common Misconceptions About Seafood Allergies

The Iodine Misconception

• A persistent misconception is that seafood allergies are related to iodine content, which has led to unnecessary concerns about cross-reactivity with iodinated contrast media 4
• This misconception likely originated from a 1975 survey where 15% of patients with contrast reactions reported shellfish allergies, but similar proportions also reported allergies to other foods like milk and eggs 4, 5
• The American College of Radiology (ACR) and American Academy of Allergy, Asthma & Immunology (AAAAI) clearly state that seafood allergies are not related to iodine content 4
• IgE-mediated reactions to crustaceans are related to tropomyosin proteins, not iodine 4, 5

Clarifying the Mechanism

• Shellfish allergies are caused by immune reactions to specific proteins (primarily tropomyosin), not to iodine 4, 2
• Iodine is not an allergen - it's a naturally occurring element to which the entire population is universally exposed 4
• The mechanism for immediate contrast media reactions is related to the physiochemical properties of the agents, not iodine content 4, 5

Food Allergies and Neurological Conditions

Current Evidence

• The available medical guidelines and research do not establish any direct relationship between seafood allergies or high IgE levels and autism spectrum disorders 4
• Food allergies can present with a variety of symptoms affecting the skin, respiratory tract, and gastrointestinal system, but neurological manifestations as primary symptoms are not typically described in the major food allergy guidelines 4
• While some patients with food allergies may experience behavioral changes during allergic reactions (likely related to discomfort or inflammatory responses), there is no evidence in the provided guidelines suggesting that seafood allergies or high IgE levels cause or worsen autism 4

Clinical Implications

Diagnosis of Seafood Allergies

• Diagnosis of seafood allergies involves obtaining a detailed history and performing in vivo and/or in vitro testing with careful interpretation of results 1
• Testing may include skin prick tests (SPT) and specific IgE measurements to identify sensitization to seafood allergens 6
• The 16.5-kD protein has been identified as having the highest frequency of IgE binding in patients with adverse reactions to shrimp, followed by the 40-kD protein 6

Management Considerations

• For individuals with confirmed seafood allergies, strict avoidance of the offending seafood is recommended 1
• Cross-reactivity between different species of molluscan shellfish has been observed, suggesting that individuals allergic to one species should avoid all molluscan shellfish 2
• Cross-reactivity with crustacean shellfish may also occur but is less clearly defined 2

Conclusion

Based on current medical evidence, there is no established relationship between seafood allergies or high IgE levels and autism spectrum disorders. The misconception linking seafood allergies to iodine has been definitively debunked, and healthcare providers should focus on accurate diagnosis and management of true food allergies based on evidence-based guidelines.