Does *Anisakis simplex* Cause Urticaria, and How Can We Manage It in Dermatology?

🔍 Key Finding Anisakis simplex, a parasite acquired from raw or undercooked seafood, can trigger both acute and chronic urticaria; however, diagnosis is challenging due to non-specific symptoms, cross-reactivity in allergy testing, and varying time intervals between ingestion and symptom onset. Recombinant allergen testing, particularly Ani s 1 and Ani s 7, offers improved specificity for diagnosing true Anisakis simplex allergy compared to whole-extract testing.

🔬 Methodology Overview

• Design: Narrative review.
• Data Sources: English-written articles from bibliographic databases (MEDLINE, PubMed, Google Scholar).
• Selection Criteria: Articles related to Anisakis simplex, urticaria, its incidence, management, and treatment in dermatological settings.
• Analysis Approach: Qualitative synthesis of findings from selected articles regarding Anisakis simplex biology, epidemiology, clinical aspects, pathogenesis, diagnosis, and treatment.
• Scope: Focus on the relationship between Anisakis simplex biology and chronic dermatological conditions like urticaria, as well as the effectiveness of systemic treatment and management in dermatology.

📊 Results

• Global anisakidosis sensitization: 27.4% in the Spanish general population and 29.8% in Japan. Higher rates (14-63%) in patients with chronic urticaria (CU).
• Italian anisakidosis data (2005-2015): Higher case numbers in central/southern regions compared to northern Italy. 40% of patients experienced allergic manifestations, with half experiencing serious reactions. Female gender independently associated with allergic manifestations and anaphylaxis.
• Italian allergy center study (2010): 4.5% of 10,570 subjects tested positive for anisakis skin prick test. 14% of those sensitized (0.6% of the total population) had a history of Anisakis simplex allergy. Sensitization rates varied geographically (0.4-12.7%), highest along Adriatic and Tyrrhenian coasts.
• Meta-analysis (1996-2017): General population sensitization to anisakis ranged from 0.4% to 27.4% (indirect ELISA/ImmunoCAP) and 6.6% to 19.6% (skin prick test). Fishermen and fish-processing workers showed higher rates (11.7-50% for specific IgE and 8-46.4% for skin prick test positivity).
• Recombinant allergen testing: Ani s 9 showed the highest specificity (98.99%) but low sensitivity (42.86%). Ani s 1 demonstrated the highest sensitivity (85.71%) with good specificity (90.91%). Combined Ani s 1 and Ani s 7 provided 100% sensitivity for gastro-allergic anisakiasis and 95% for A. simplex sensitization-associated CU. Ani s 13 (anisakis haemoglobin) was detected in 72.1% of sensitized patients by indirect ELISA.

💡 Clinical Impact Dermatologists should consider anisakiasis in patients presenting with acute or chronic urticaria, especially with a history of raw or undercooked fish/squid consumption, to ensure appropriate management and prevent severe allergic reactions. This awareness may prompt earlier investigation with specific IgE testing against recombinant Anisakis allergens, improving diagnostic accuracy and guiding appropriate interventions.

🤔 Limitations

• Real burden of anisakidosis is still not completely known and probably underestimated.
• Low specificity of skin prick tests and IgE testing with anisakis whole extracts due to cross-reactivity with other nematode species or allergen sources.
• Difficulty in evaluating the clinical relevance of Anisakis simplex sensitization associated with CU and possible previous parasitism.
• Difficulty in diagnosing anisakidosis if endoscopy is delayed.
• Limited data on albendazole usage in pregnancy.
• Molecular diagnostic methods are not yet widely available.

✨ What It Means For You Dermatologists should consider anisakiasis in patients presenting with acute or chronic urticaria, especially if there is a history of raw or undercooked fish/squid consumption. Testing for specific IgE against recombinant Anisakis allergens (Ani s 1 and Ani s 7) offers improved diagnostic accuracy over crude extracts and can guide appropriate management, including potential gastroenterological referral.

Reference Javor S, Bignardi D, Borro M, Massone C. Anisakis simplex and urticaria. What we know about its real incidence and management in dermatological settings? Dermatology Reports. 2024;16:9819. https://doi.org/10.4081/dr.2023.9819