Fish allergy time of sensitization - what is the explanation for the increased prevalence of fish allergy in adults compared to children? Given the fact that the introduction of fish in the diet takes place during the first 1-3 years of life, someone would expect the prevalence of fish allergy to be equal or smaller in adults. Is there any reference showing that sensitization can happen later in life? Thank you.


Thank you for your inquiry.

Actually, food allergy in general is increasing both in the adult and pediatric population. It is true that fish allergy is slightly more common in adults than in children, and shellfish allergy is far more common in adults than in children (see abstract by Sicherer, et al., and information copied below). The reasons for this are unclear. They are complex, as you can see from the abstracts below indicating some studies have suggested the early introduction of fish is protective against fish allergy, whereas in the past, it has been assumed that the early introduction of fish would predispose to fish allergy at an early age.

The issues surrounding early versus later introduction have not been settled at this time. So we cannot give you a definitive answer as to why fish allergy is more common in adults, but it is assumed that shellfish allergy is more common in adults because of the much later introduction of shellfish into the diet.

However, it is clear that allergies to foods can develop de novo in adults. The reference by Bahna copied below (1) discusses this to some extent.

In regards to the observation that food allergy can develop in adults, I have copied below an abstract by Kivity, et al., which describes characteristics of late onset food allergy and discusses the issue of onset of allergy later in life. It is quite clear that allergy can develop, for the first time, in adulthood.

Thank you again for your inquiry and we hope this response is helpful to you.

1. Bahna SL. You can have fish allergy and eat it too! Journal of Allergy and Clinical Immunology, July 2004; 114(1):125-126.

Prevalence of seafood allergy in the United States determined by a random telephone survey.
Sicherer SH, Muñoz-Furlong A, Sampson HA.
Elliot and Roslyn Jaffe Food Allergy Institute, Division of Allergy and Immunology, Department of Pediatrics, Mount Sinai School of Medicine, New York, NY 10029-6574, USA.
Background: Seafood allergy is potentially severe, but the prevalence of this group of food allergies in the US population has not been determined.
Objective: To estimate the prevalence of seafood (fish, shellfish) allergy in the United States.
Methods: We performed a nationwide, cross-sectional, random telephone survey by using a standardized questionnaire. Criteria were established in advance to define seafood allergy by report of convincing symptoms and physician evaluation.
Results: A total of 5529 households completed the survey (67.3% participation rate), representing a census of 14,948 individuals. Fish or shellfish allergy defined by established criteria was reported in 5.9% (95% CI, 5.3%-6.6%) of households and among individuals as follows: 2.3% (95% CI, 2%-2.5%) for any seafood allergy, 2% for shellfish, 0.4% for fish, and 0.2% for both types. Seafood allergy was more common in adults compared with children (2.8% vs 0.6%; P <.001) and in women compared with men (3.6% vs 2%; P <.001). Recurrent reactions were reported by 58%, dyspnea or throat tightness was reported by more than 50%, and 16% were treated with epinephrine. Despite this level of acuity, only 8.6% were prescribed self-injectable epinephrine. The rate of reactions to multiple fish among those with any fish allergy was 67%; for Crustacea the rate was 38%, and for mollusks the rate was 49%; only 14% with crustacean allergy reported a mollusk allergy.
Conclusions: Physician-diagnosed and/or convincing seafood allergy is reported by 2.3% of the general population, or approximately 6.6 million Americans. Affected individuals typically report recurrent and sometimes severe reactions, indicating that seafood allergy represents a significant health concern.

Curr Allergy Asthma Rep. 2005 Jan;5(1):74-9.
Fish and shellfish allergy.
Wild LG, Lehrer SB.
Tulane University Health Sciences Center, 1430 Tulane Avenue, SL-57, New Orleans, LA 70112, USA.
Fish and shellfish are important in the American diet and economy. Nearly $27 billion are spent each year in the United States on seafood products. Fish and shellfish are also important causes of food hypersensitivity. In fact, shellfish constitute the number one cause of food allergy in the American adult. During the past decade, much has been learned about allergens in fish and shellfish. The major allergens responsible for cross-reactivity among distinct species of fish and amphibians are parvalbumins. The major shellfish allergen has been identified as tropomyosin. Many new and important potential cross-reacting allergens have been identified within the fish family and between shellfish, arachnids, and insects. Extensive research is currently underway for the development of safer and more effective methods for the diagnosis and management of fish and shellfish hypersensitivity.

Shellfish allergy is the most common allergy in Canada, affecting 1.42 per cent of the population. Most sufferers are adults: 1.69 per cent have the allergy, compared to just 0.5 per cent of children.

Fish allergy is less common, affecting 0.18 per cent of children and 0.56 per cent of adults.

In general, food allergy is on the rise in North America and other developed countries In Canada, an estimated 7.5 per cent of people have food allergies, representing more than 2.5 million people. In the United States it’s estimated that 12 million Americans (or just under 4 per cent of the population) have food allergies.

A major study in the United States recently found that cases of peanut allergy in children more than tripled in a decade, and that more than 3 million Americans now have a peanut or nut allergy.

Here are the rates of some of the major allergens in Canada and the U.S.







1.68 %

0.71 %

0.93 %

Tree Nut

1.59 %

1 %

1.14 %


0.5 %

1.69 %

1.42 %


0.18 %

0.56 %

0.48 %


0.23 %

0.05 %

0.09 %


Source: Surveying Canadians to Assess the Prevalence of Common Food Allergies and Attitudes towards Food LAbelling and Risk (SCAAALAR) study. Published in the Journal of Allergy and Clinical Immunology, June 2010.






Tree Nut





Peanut, Tree Nut or both:
Children - 2.1 %
Adults – 1.3 %
Source: US prevalence of self-reported peanut, tree nut, and sesame allergy: 11-year follow-up. Published in the Journal of Allergy and Clinical Immunology, June 2010

Acta Paediatr. 2010 Dec;99(12):1861-7. doi: 10.1111/j.1651-2227.2010.01939.x.
Early fish introduction is associated with less eczema, but not sensitization, in infants.
Hesselmar B, Saalman R, Rudin A, Adlerberth I, Wold A.
Department of Paediatrics, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
Objective: To investigate if the development of allergic diseases during the child's first 18 months of life is influenced by the time at which different food items were introduced into the child's diet.
Method: A birth cohort of 184 children was followed to 18 months of age. Diaries were used to document feeding practices, and parental interviews were performed at 6 and 12 months of age, probing for symptoms suggesting allergic disease, general health-related issues and food introduction regimes. Symptoms promoted prompt clinical examination, and all children were examined clinically, and tested for sensitization to common airborne and food allergens at 18 months of age.
Results: The earlier the fish was introduced into the child's diet the lower was the frequency of eczema. This association remained after control for confounding factors. The timing of fish introduction and asthma development showed a similar pattern, but did not reach statistical significance. Sensitization was not influenced by the timing of fish introduction. Other food items or feeding practices did not seem to influence allergy development.
Conclusion: Early  less introduction of fish into the child's diet was associated with eczema development, and a tendency to less asthma. Sensitization was not associated with the timing of fish introduction.

Allergy. 2006 Aug;61(8):1009-15.
Fish consumption during the first year of life and development of allergic diseases during childhood.
Kull I, Bergström A, Lilja G, Pershagen G, Wickman M.
Occupational and Environmental Health, Stockholm County Council, Stockholm, Sweden.
Background: Fish consumption during infancy has been regarded as a risk factor for allergic disease but later evidence suggests a protective role. However, methodological limitations in the studies make conclusions uncertain. The aim of this study was to assess the association between fish consumption during the first year of life and development of allergic diseases by age 4.
Methods: A prospective birth cohort of 4089 new-born infants was followed for 4 years using parental questionnaires at ages 2 months, 1, 2 and 4 years to collect information on exposure and health effects. The response rate at 4 years was 90%. A clinical investigation was performed at age 4 years, which included blood sampling for analysis of specific IgE to common food and airborne allergens.
Results: Parental allergic disease and onset of eczema or wheeze during the first year of life delayed introduction of fish in the child's diet. After exclusion of such children to avoid disease-related modification of exposure, regular fish consumption during the first year of life was associated with a reduced risk for allergic disease by age 4, OR(adj) 0.76 (95% CI 0.61-0.94) and sensitization, OR(adj) 0.76 (0.58-1.0). The reduced risk appeared most pronounced for multiple disease, OR(adj) 0.56 (0.35-0.89). IgE-sensitization to fish was only present among 18 of the 2614 children.
Conclusion: Regular fish consumption before age 1 appears to be associated with a reduced risk of allergic disease and sensitization to food and inhalant allergens during the first 4 years of life.

The pattern of food hypersensitivity in patients with onset after 10 years of age

Clinical & Experimental Allergy
Volume 24, Issue 1, pages 19–22, January 1994
One hundred and twelve patients with a history of immediate adverse reaction after food ingestion and positive skin test to food are presented with the result of food challenge. In all patients the symptoms started after 10 years of age; most presented with recurrent short-lasting urticarial rash, often accompanied by rhinitis. In the majority of the patients, skin tests were positive to multiple food allergens, but 67% of these responded to oral provocation by only one allergen. One-third of the patients had a history of allergic symptoms following exercise after meals, but in only one-third of these symptoms were reproducible in the laboratory. Fruit and vegetables were the main allergens responsible for food hypersensitivity. Food allergy can develop after the first 10 years of life. Fruit and vegetables are the main cause of food allergy in these patients, while milk and egg are the least common. These findings differ from those in early childhood where milk and eggs are the main allergens.

Phil Lieberman, M.D.

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