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Fish Allergy: Overview, Diagnosis, and Treatment

About Fish Allergy

It is estimated that up to 0.2 percent of the general population is affected by fish allergy.1,2 Fish allergy does occur in children, but is more prevalent in adolescents and adults: Nearly 40 percent of patients with fish allergy first react during adulthood.3 Because fish allergy is often noted in adults, it is considered a life-long allergy that is not usually outgrown.3-5

Patients become sensitized to fish in the following ways: By exposure via the gastrointestinal tract during ingestion (the major route of sensitization), via the respiratory system by aeroallergens (an important trigger of atopic dermatitis), or by skin contact.2 For 8.6 percent of patients with fish allergy, the worst reactions were to skin contact and/or inhalation, and some of these patients were able to eat fish without reaction.3

Seafood allergy, including fish, is potentially severe, and in some cases, can even lead to life-threatening anaphylaxis.2,3

40% of patients


Nearly 40 percent of patients with fish allergy first react during adulthood.3
 

Common clinical manifestations of fish allergy include:2

  • Oral allergy syndrome
  • Rhinitis
  • Abdominal pain
  • Diarrhea
  • Urticaria
  • Angioedema
  • Asthma

Identifying individuals with fish allergy is important, as these patients are at risk for severe reactions.2,3

Fish allergy: Refining differential diagnosis through testing

The current clinical approach to fish allergy diagnosis includes a physical examination, skin-prick testing or specific IgE blood testing, and, in selected cases, an oral food challenge.1,2 Like all food allergies, diagnosing a fish allergy starts with a physical examination and, of critical importance, a food-allergy-focused patient history.6,7

The findings of this fish-allergy-focused patient history can be used to guide testing decisions and results interpretation. 

This systematic approach can help determine whether the reported history of food allergy, combined with laboratory data, is sufficient to diagnose fish allergy, or if an oral food challenge should be considered.1,8
 

Who should be tested?

Identifying individuals with fish allergy is important, as these patients are at risk for severe reactions.2,3 Allergy to fish is usually lifelong, making effective and accurate diagnostic workup for seafood allergy essential for clinicians and patients.1,3-5

Click to View Algorithm

The evaluation for a patient with a possible food allergy begins with a thorough history and physical exam. If the clinical history suggests an IgE-mediated food allergy, skin-prick or specific IgE tests are needed to help confirm the diagnosis. Algorithm data from Niggemann and Beyer and Lopata et al.

Fish allergy and quality of life

Food allergy, including fish allergy, can have a dramatic effect on quality of life.9 Many studies have detailed the negative effect of food allergy on health-related quality of life (HRQoL), as well as the financial and emotional toll a food allergy takes.8 Identified issues include feeling different because of the diet, worrying about foods, the presence of physical and emotional distress, increased responsibility, effect on social activities (social restrictions, school, travel, and dining out), anxiety, stress, bullying, and having to consistently exercise greater caution.8

Where fish can be found

Fish can be found in processed foods in raw, powder, or oil form.10

Fish may be found in Caesar salad dressing and in Worcestershire sauce if they contain anchovies.10 It has been reported that fish allergens hidden in other foods caused reactions in 35 percent of patients with fish allergy.11

 

Cross-reactivity

The diagnosis of fish allergy is complicated by cross-reactivity among fish allergens.1 Clinical cross-reactivity among fish species is common, even in fish from taxonomically distinct orders.1 Patients allergic to finned fish (e.g., tuna, salmon, and cod) may need to avoid that entire food group because of high rates of cross-reactivity.5 Allergic cross-reactivity among fish is high, but variable: Patients may have clinical monosensitivity to a single fish or fish family, for example, only to swordfish.1,5,11

Testing Confidence

Testing Increases Diagnostic Confidence

Adding diagnostic testing to aid in a differential diagnosis has been shown to increase confidence in diagnosis to 90 percent.i,ii Conventionally, a diagnosis of allergic or autoimmune disease relies on the case history and a physical examination. However, adding diagnostic testing to aid in a differential diagnosis has been shown to increase confidence in diagnosis.i,ii Diagnostic testing can also help to improve the patient’s quality of life and productivity, reduce costs associated with absenteeism, and optimize use of medication, in addition to decreasing unscheduled healthcare visits.iii,iv 

i. Duran-Tauleria E, Vignati G, Guedan MJ, et al. The utility of specific immunoglobulin E measurements in primary care. Allergy. 2004;59 (Suppl78):35-41.
ii. NiggemannB, Nilsson M, Friedrichs F. Paediatric allergy diagnosis in primary care is improved by in vitro allergen specific IgE testing. Pediatr Allergy Immunol. 2008;19:325-331
iii. Welsh N, et al. The Benefits of Specific Immunoglobulin E Testing in the Primary Care Setting. J Am Pharm Assoc. 2006;46:627.
iv. Szeinbach SL, Williams B, Muntendam P, et al. Identification of allergic disease among users of antihistamines. J Manag Care Pharm. 2004; 10 (3): 234-238

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Management and care of patients with fish allergy

Currently, optimal management of seafood allergy does not exist. The management of fish allergy relies on the elimination of fish from the diet of the sensitized patient and symptomatic treatment of accidental allergic reactions.2, 11 As manifestations of fish allergy may be life-threatening and are frequently life-long, patients with potentially life-threatening food allergy should be prescribed an epinephrine auto-injector and educated in its use.5

Practice parameters have been developed to help guide the management and treatment of patients with food allergies, including fish.

References
  1. Tong WS, Yuen AW, Wai CY, Leung NY, Chu KH, Leung PS. Diagnosis of fish and shellfish allergies. J Asthma Allergy. 2018;11:247–260.
  2. Kuehn A, Swoboda I, Arumugam K, Hilger C, Hentges F. Fish allergens at a glance: variable allergenicity of parvalbumins, the major fish allergens. Front Immunol. 2014 Apr 22;5:179
  3. Sicherer SH, Muñoz-Furlong A, Sampson HA. Prevalence of seafood allergy in the United States determined by a random telephone survey. J Allergy Clin Immunol. 2004 Jul;114(1):159-65.
  4. Wood RA: The natural history of food allergy. Pediatrics. 2003, 111 (6 Pt 3): 1631-1637.
  5. Abrams EM, Sicherer SH. Diagnosis and management of food allergy. CMAJ. 2016;188(15):1087–1093.
  6. Kurowski K, Boxer RW. Food allergies: detection and management. Am Fam Physician. 2008;77:1678-1688. 
  7. Burks AW, Tank M, Sicherer S, et al. ICON: Food allergy. J Allergy Clin Immunol. 2012;129:906-920. 
  8. Sicherer SH, Sampson HA. Food allergy: A review and update on epidemiology, pathogenesis, diagnosis, prevention, and management. J Allergy Clin Immunol. 2018 Jan;141(1):41-58.
  9. Antolín‐Amérigo et al. Quality of life in patients with food allergy. Clin Mol Allergy. 2016;14:4.
  10. Steinman HA. "Hidden" allergens in foods. J Allergy Clin Immunol. 1996 Aug;98(2):241-50.
  11. Prester L. Seafood Allergy, Toxicity, and Intolerance: A Review. J Am Coll Nutr. 2016;35(3):271-83.