Sardine
Summary
Sardines (Sardina pilchardus, Sardinops sagax and related species) are members of the herring family found in the Atlantic, Pacific and Mediterranean seas. Fish is an ingested, contact and inhalant allergen; parvalbumin proteins in muscle tissue are the most common allergenic component. Fish allergy is seen more frequently in children than adults and is often severe, producing a range of cutaneous, gastrointestinal, cardiovascular and respiratory symptoms as well as anaphylaxis. Cross-reactivity occurs between bony fish species, although this is not always clinically significant.
Epidemiology
Worldwide distribution
In a Dutch study, only 59% of 38 fish-allergic patients reported a reaction to all fish species ever tried, with the rest tolerating one or more species. Fifteen patients had tried sardine and of these, nine (60%) showed allergic symptoms. Sardine was the most common fish causing adverse reactions in a survey of 1,008 Moroccan hospital patients.
Pediatric issues
In a Portuguese study of 81 fish-allergic patients, 95% developed symptoms before the age of 18 years (mean age 24.2 months) and sardine was among the five most common species associated with allergic reactions.
In a Moroccan survey of 2,802 high school children, 266 (9.5%) reported fish/shellfish allergy. Of these the most prevalent fish species was sardine, reported by 74.1% of fish-allergic children. The most frequently reported symptoms were cutaneous, followed by gastrointestinal and respiratory symptoms. Children who had been breast-fed in infancy were significantly less likely to be allergic to sardine than those who were not breast-fed.
Route Of Exposure
Main
The main route of exposure is ingestion of fish meat.
Secondary
Fish can also be a contact and inhalant allergen. Occupational asthma has been linked to inhalation of aerosolized, blood-derived allergens during processing of fish.
Clinical Relevance
Parvalbumins from fish are major food allergens causing IgE responses in most fish-allergic individuals. In most cases, symptoms are reported after the first contact with fish. Reactions range from mild local instances, to severe, acute respiratory or cardiovascular symptoms, and include rhinoconjunctivitis, oral allergy syndrome, angioedema, urticaria, emesis, diarrhea, hoarseness, dyspnea, stridor, tachycardia and anaphylaxis.
As well as ingestion, patients may be sensitized to fish via direct skin contact or by inhalation of fish steam during cooking or processing. In a Greek study examining changes in fish tolerance with age, 26 of 45 fish-allergic children (58%) reacted after skin contact with fish and 18 (40%) reacted after inhalation of fish. Skin prick tests to sardine showing wheals greater than 6.5 mm were a positive predictive marker for fish allergy in 92% of the study cohort.
Prevention And Therapy
Prevention strategies
Contrary to other sources, a Moroccan study demonstrated that certain types of processing (fermentation, marinading or canning) reduced sardine immunoreactivity significantly compared to raw fish extract, as measured by differential IgE binding. In a similar study, heating and pepsin digestion were also found to reduce immunoreactivity to sardine parvalbumin.
Cross-Reactivity
There is significant (62–74%) structural homology among ß-parvalbumin isoforms of different bony fish species, leading to a high degree of cross-reactivity. However, despite frequent serological cross-reactivity, clinical relevance may be limited to only certain species; for example, a Dutch study found the inter-species specificity of specific IgE was 75% for sardine and 0% for hake, pollock and swordfish.
As well as parvalbumin homology, another cause for cross-reactivity could be the presence of other potentially allergenic proteins such as enolases, aldolases and fish gelatin.
References
- LOINC. Sardina pilchardus 2006 [cited 2022 10.01.22]. Available from: https://loinc.org/63134-1/.
- CABI. Sardina pilchardus Wallingford, UK 2019 [cited 2022 10.01.22]. Available from: https://www.cabi.org/isc/datasheet/65375.
- CABI. Sardinops sagax Wallingford, UK2019 [cited 2022 10.01.22]. Available from: https://www.cabi.org/isc/datasheet/65610.
- Matricardi PM, Kleine-Tebbe J, Hoffmann HJ, Valenta R, Hilger C, Hofmaier S, et al. EAACI Molecular Allergology User's Guide. Pediatr Allergy Immunol. 2016;27 Suppl 23:1-250.
- Schulkes KJG, Klemans RJB, Knigge L, de Bruin-Weller M, Bruijnzeel-Koomen CAFM, Marknell deWitt Å, et al. Specific IgE to fish extracts does not predict allergy to specific species within an adult fish allergic population. Clinical and Translational Allergy. 2014;4(1):27.
- Mejrhit N, Azdad O, El Kabbaoui M, Ouahidi I, Tazi A, Aarab L. Sensitivity of Moroccans to sardine parvalbumin and effect of heating and enzymatic treatments. Food and Agricultural Immunology. 2017;28(6):1362-73.
- Carvalho S, Marcelino J, Cabral Duarte MF, Costa C, Barbosa MA, Pereira Dos Santos MC. Role of Recombinant Parvalbumin Gad c 1 in the Diagnosis and Prognosis of Fish Allergy. J Investig Allergol Clin Immunol. 2020;30(5):340-5.
- Mejrhit N, Azdad O, Aarab L. Effect of industrial processing on the IgE reactivity of three commonly consumed Mo-roccan fish species in Fez region. Eur Ann Allergy Clin Immunol. 2018;50(5):202-10.
- LOINC. Sardine (Sardinops melanosticta) IgE Ab [Units/volume] in Serum 2006 [cited 2022 10.01.22]. Available from: https://loinc.org/30989-8/.
- Pascual CY, Reche M, Fiandor A, Valbuena T, Cuevas T, Esteban MM. Fish allergy in childhood. Pediatric Allergy and Immunology. 2008;19(7):573-9.
- Xepapadaki P, Christopoulou G, Stavroulakis G, Freidl R, Linhart B, Zuidmeer L, et al. Natural History of IgE-Mediated Fish Allergy in Children. J Allergy Clin Immunol Pract. 2021;9(8):3147-56.e5.
- Allergome. Pilchard 2021 [cited 2022 10.01.22]. Available from: http://www.allergome.org/script/search_step2.php.
- Allergome. Sardine 2021 [cited 2022 10.01.22]. Available from: http://www.allergome.org/script/search_step2.php.