Summary

Tuna is an important wild-caught fish found in tropical and subtropical oceans. They can survive at a temperature cooler than 5°C and have pantropical and warm-temperate distribution. Tuna is largely found in the Pacific, Indian, and Atlantic Oceans in the inter-tropical zone. Worldwide, fish allergy prevalence is 0.2%. Fish allergy prevalence is higher in countries where fish is consumed as staple food and where a high number of fish-processing industries are found. Tuna is widely consumed in the US, Europe, and other countries around the world. Tuna allergy is primarily induced through oral route and secondarily through exposure to vapors while cooking and boiling fish or fish processing and through contact. In sensitized individual tuna fish allergens are reported to induce oral allergy syndrome, angioedema, urticaria, nausea, vomiting and abdominal pain, ocular or upper respiratory symptoms such as rhinorrhea and nasal pruritus, and even occupational asthma and rhinitis. The major allergen in tuna fish is Thu a 1, a parvalbumin, which is a highly stable and heat resistant protein found in fish muscle. Fish parvalbumin is a panallergen, which is responsible for cross-reactivity among different fish species. Patients allergic to tuna may show 50% cross-reactivity with salmon and cod. Cross-reactivity between finned fish and shellfish such as crustaceans is also reported. Fish allergic individuals are advised to avoid fish in any form from the diet.

Epidemiology

Worldwide distribution

Prevalence of fish allergy is found to be higher in countries where there is high fish consumption and also many fish-processing industries are found. Fish allergy prevalence is 0.2% worldwide, while in the United States (US) the prevalence was 0.4%, and among Asian countries, the Philippines (2.29%) has the highest fish allergy prevalence compared to Singapore (0.26%) and Thailand (0.29%). In European countries, the prevalence of fish allergy in the adult population was found to be about 0.8% and is a little higher than the children. The countrywide prevalence of clinically confirmed fish allergy in the pediatric population in Europe was found to be 0.7 % in Sweden (4 years old), 0.6% in Germany (2-6 years old), and 5% in Finland (1-4 years old). In Norway, fish allergy prevalence is reported to be 0.1%. A nationwide, cross-sectional, random telephone survey performed in the US found that seafood allergy is reported by 2.3% of the general population and among them, 2% was for shellfish, 0.4% for fish, and 0.2% for both types.

A study by Turner et al. (2011) in Australia reported IgE-mediated fish allergy in 95 out of a total of 167 children with a history of food or seafood allergy. Among these fish allergic patients, 38 children were found to be allergic to salmon or tuna. In the USA, salmon along with tuna, catfish, and cod are the most important species reported for causing allergy followed by flounder, halibut, trout, and bass. In Australia, a retrospective study among 2,999 food-allergic children, showed 5.6% fish allergy prevalence and tuna and salmon were most commonly associated with this allergy.

A retrospective study by Khan et al. (2011) in the US evaluated 5162 adult patients (≥18 years) with seafood allergy and found the fish allergy prevalence to be 13.8%. Among the fish allergy patients, the prevalence of tuna allergy was found to be highest, which was about 28.6%.

Route Of Exposure

Main

The primary route for tuna allergen exposure is through oral route (ingestion).

Secondary

Exposure to vapor (inhalation of wet aerosols) while cooking and boiling fish or fish processing, such as fish heading, degutting in food processing units is reported to induce allergic reactions in sensitized individuals, and also handling of fish may induce dermatitis via skin contact.

Clinical Relevance

Oral allergy symptoms and Anaphylaxis

Sensitization to fish usually begins at the childhood stage and the patients mostly remain allergic in their entire life. Fish allergic patients on ingestion of fish or on coming in contact with fish or fish products may develop a single symptom or several clinical manifestations including urticaria and eczema. Clinical symptoms may occur in a single organ or multiple organs and can be mild to severe anaphylaxis. Clinical manifestations of fish allergy typically include:

A retrospective study by Turner et al. (2011) analyzed 167 seafood allergic children and reported that tuna and salmon were the most common fish allergens. About 21% of children had reported anaphylaxis to fish. After eating tinned fish, 12 (32%) children developed symptoms among which two children reported anaphylaxis. Among 26 children, 8 (31%) tolerated canned fish while they had reported allergic reactions such as angioedema, and urticaria to fresh fish. Gastrointestinal symptoms such as nausea, vomiting, and abdominal pain were reported in 12% of children. Also, among all the tuna and/or salmon allergic children, 21% were able to tolerate a canned form of fish.

In one US study with 5162 seafood allergic patients, skin manifestation was most commonly reported by the fish allergic patients, followed by respiratory manifestations. Among 6 tuna allergic patients, 5 showed symptoms related to skin, 2 showed respiratory symptoms, and 1 showed eye/nasal symptoms.

A case study reported about a 57-year-old hypertensive man with a history of allergy, presented with facial rash, and palpitations on ingestion of canned tuna fish. On further tests, the patient was diagnosed with Kounis syndrome, a complex cardiovascular problem following allergy or hypersensitivity, and anaphylactic shock.

In another case study, a 19-year-old man was presented with body flushing and itching with facial and throat swelling, after 15 to 30 minutes of eating beans, peas, chicken, turkey, and canned tuna. Based on diagnostic tests and history, he was found allergic to canned tuna, indicating that canned tuna can also cause allergy in sensitive individuals.

Allergic rhinitis

Occupational exposure to wet aerosols from fish heading and degutting, and boiling fish in sensitized workers can lead to respiratory symptoms such as asthma, rhinitis, dyspnea, wheezing, tightness of the throat, and even skin rash. Ocular or upper respiratory symptoms such as rhinorrhea and nasal pruritus induced by vapor from seafood were reported in 16% of children.

Asthma

Occupational exposure to tuna at the workplace is reported to induce asthma and dermatitis; however, anaphylaxis was rare in occupationally exposed workers. Inhalation of vapor during cooking and processing seafood can induce upper and lower airway symptoms.

Atopic Dermatitis

Fish aeroallergens may be majorly responsible for triggering atopic dermatitis.

Other diseases

Histamine food poisoning:

Histamine food poisoning is a type of allergy-like food poisoning occurred after eating fish or fermented foods. A high level of histidine present in fish muscles act as a substrate for bacterial histidine decarboxylase, which converts histidine to histamine. Histamine cannot be destroyed by freezing, or smoking, or even cooking. A study by Velut et al. (2019) showed yellowfin tuna induced histamine food poisoning in a French military unit near Paris. A total of 40 cases (attack rate: 16.6%) were identified and then a case-control study was performed with 31 cases and 63 controls. It was found that cooked yellowfin tuna fillet was the major source of histamine food poisoning. The typical symptoms were reported to be mild and of short duration, including flushing, cutaneous rash, or headache and the symptoms appear within 1 hour of ingestion of tuna fish.

Prevention And Therapy

Prevention strategies

Avoidance

If an individual is suffering from a fish allergy, it is advisable to avoid fish in any form from the diet.

Cross-Reactivity

Patients allergic to finned fish such as tuna may show 50% cross-reactivity to other finned fishes (e.g. salmon and cod). Fish parvalbumin is a panallergen, which shows cross-reactivity among closely related fishes. Allergens from tuna and pollack (The c 1) are highly cross-reactive to salmon allergens. Few case reports have mentioned mono-sensitization to tuna. Moreover, few fish allergic patients are known to develop an allergy to creatine kinase from tuna.

Minor allergens β-enolases and the aldolases are also reported to cross-react, but reactivity differs from individual to individual.

Shellfish (shrimp and lobster) or finned fish allergic patients are recommended to avoid all the species of shellfish or finned fish due to the high rate of cross-reactivity.