f369 Catfish

Summary

Catfish belong to the order Siluriformes, which encompasses several families, including genera like Ictalurus and Pangasius. Catfish are significant in aquaculture and fisheries, providing food and economic value. Ingestion is the primary route of exposure to catfish allergens, leading to symptoms ranging from mild oral allergy reactions and localized urticaria to severe anaphylactic responses. The major fish allergen parvalbumin has been detected in catfish. IgE cross-reactivity between allergens from catfish and other fish species—such as tilapia, tuna, herring, salmon, halibut, grass carp, cod, and grouper, has been documented. Cross-reactivity between catfish allergens within the order Siluriformes can be expected. Diagnosis of fish allergy involves evaluating the patient’s medical history along with diagnostic tests such as specific IgE measurements and skin prick tests. Oral food challenge is sometimes performed when deemed necessary. Management of fish allergies typically involves avoiding foods that contain fish products.

Allergen

Nature

Catfish belong to the order Siluriformes, which encompasses several families, including Pangasiidae and Ictaluridae. Pangasiidae, primarily found in Southeast Asia, includes genera like Pangasius. Ictaluridae, native to North America, includes genera such as Ictalurus.

The channel catfish (Ictalurus punctatus) is a commercially important species for aquaculture and sport angling (Haubrock et al. 2021). It has a slender, scaleless body with typical coloration ranging from white or silvery on the underside to grayish-blue or olive, and sometimes nearly black on the back (Tucker 2012). Channel fish have eight barbels—four dorsal and four ventral—around their subterminal mouth. Although their fins are soft-rayed, sharp spines are present on both the pectoral and dorsal fins. A characteristic feature of the channel catfish is its deeply forked tail, although the depth of the fork tends to diminish in older fish, especially in large breeding males. In the wild, it typically takes 2–4 years for a channel catfish to reach a weight of 0.5 kg, although growth rates vary depending on factors such as temperature and food availability. These fish can grow over 20 kg in weight and may live for more than 20 years. They are opportunistic omnivores and consume food based on availability (Tucker 2012).

Habitat

Channel catfish thrive in a range of habitats, including clear, fast-moving streams as well as slow-moving rivers, lakes, and ponds. They are bottom-dwellers that prefer sand and gravel substrates (Tucker 2012).

Taxonomy

The channel catfish belongs to the family Ictaluridae, which includes seven genera and at least 45 species. While many ictalurids are considered good table fish, channel catfish account for nearly all commercial food fish production (Tucker 2012). The taxonomic tree of I. punctatus is shown in the table below (NCBI-NIH 2020):

Tissue

Fish are a primary source of long-chain polyunsaturated fatty acids (LC-PUFAs), which offer several nutritional benefits. Catfish is rich in linoleic acid as well as LC-PUFAs (Parra-Bracamonte et al. 2024). β-parvalbumin is the major allergen present in bony fish (Kalic et al. 2021). The parvalbumin beta gene has been found in channel catfish and the protein is mainly responsible for muscle relaxation (Kim 2003, Buyuktiryaki et al. 2021). While parvalbumin is primarily found in muscle tissue, it is also expressed in other tissues such as nervous tissue, testis, and endocrine glands (Kim 2003).

Epidemiology                                  

Worldwide distribution

Fish is a frequent cause of food allergies, especially in coastal areas where the supply of fish is high (Leung et al. 2024). Prevalence varies across regions, with some Asian countries, such as the Philippines (2.3%) and Korea (12.5%), reporting higher prevalence than the U.S. (< 0.5%) (Oh et al. 2004, Sicherer et al. 2004, Connett et al. 2012, Schulkes et al. 2014).

A multicenter, retrospective observational study conducted between 2015 and 2019 analyzed 945 patients (age range: 0–90 years) with seafood allergies from seven hospitals in the US and the UK. Of these, 694 were from the U.S. and 251 from the U.K. Fish allergy prevalence among U.S. patients was 45.8% (318/694), while only 7.6% (19/251) of U.K. patients were affected. Among the 645 U.S. patients with available sensitization data, 5.4% tested positive for specific(s) IgE to fish allergens, with 2.9% testing positive specifically for catfish. On the other hand, of the 185 U.K. patients with available sensitization data, 52.4% had a positive specific IgE to at least one fish allergen. The most common fish causing allergies were cod, salmon, mackerel, and tuna (Nakonechna et al. 2024).

Another U.S.-based retrospective study involving 5,162 patients (aged ≥ 18 years) conducted during 1997–2010 found that 640 patients had physician-recorded food allergies. Of these, 24.8% (159/640) had a seafood allergy. Among those with seafood allergies, 22 patients (13.8%) were allergic to fish. Tuna was the most common trigger of allergy (28.6%), followed by catfish (23.8%) and salmon (23.8%) (Khan et al. 2011).

Risk factors

The presence of concomitant asthma and eczema are common risk factors for fish allergy (Mourad et al. 2015). A study involving 249 children (median age: 4.2 years) with a history of fish allergy and confirmed sensitization through skin prick test (SPT) or specific IgE testing, reported a significant correlation between catfish-specific IgE levels and the severity of atopic dermatitis (AD) (Leung et al. 2024).

Pediatric issues

Fish allergy often continues into adulthood and is recognized as a trigger of anaphylaxis in young children (Leung et al. 2024). A cross-sectional study conducted in Thailand on 11 children (median age: 3 years) with IgE-mediated fish allergies reported catfish (4/11) and tilapia (4/11) as the most common triggers, followed by salmon (3/11). The levels of specific IgE to catfish in ten of the children in the study ranged from 0.23 to 22.6 kU_A/L. The IgE levels for catfish, salmon, cod, tilapia, and tuna in the remaining child were measured at 0 to 0.06 kU_A/L. (Tangvalelerd et al. 2025).

Another study involving 249 children (median age: 4.2 years) with a history of fish allergy and confirmed sensitization found that the median specific IgE levels for tilapia (4.88 kU_A/L) and catfish (4.35 kU_A/L) were higher than those for most other fish species, which generally had specific IgE levels below 4 kU_A/L. Notably, catfish was identified as one of the least tolerated fish among these children (Leung et al. 2024).

Environmental characteristics       

Living environment

Channel catfish can tolerate a wide range of environmental conditions. Native to temperate climates, they are well-adapted to grow and thrive across a broad temperature spectrum. The ideal water temperature for growth ranges between 25°C and 30°C, though they can survive in temperatures from just above freezing up to around 40°C. Their growth slows at temperatures below 20°C, and feeding activity ceases at temperatures below approximately 10°C. Their tolerance to salinity also varies depending on their life stage. While eggs can tolerate salinity levels as high as 16%, this tolerance decreases to 8% at hatching and then increases to a maximum of about 12% in adults. In adult fish, growth begins to slow when salinity exceeds about 6% (Tucker 2012).

Worldwide distribution

The channel catfish is a popular food fish in North America and is widely cultivated in aquaculture facilities in U.S and China. Native to central North America, its natural range extends from the Rocky Mountains to the Appalachian Mountains and from the Gulf of Mexico to the Hudson Bay drainage (Tucker 2012). Channel catfish have been extensively introduced across North America, as well as in Europe, Russia, Cuba, and parts of Latin America (FAO 2009, Tucker 2012).

Route of Exposure

Main

Ingestion is the primary route of exposure to catfish allergens, leading to allergic reactions in sensitized individuals (James et al. 1997, Khan et al. 2011).

Clinical Relevance

Bony fish, such as catfish, cod, and salmon, are more commonly associated with allergies due to their higher allergen content compared to cartilaginous fish like shark, ray, and ghost sharks (Dong et al. 2022). Exposure to these allergens can trigger allergic reactions affecting multiple organ systems, with symptoms varying from mild oral allergy symptoms and localized urticaria to severe anaphylactic reactions (Kalic et al. 2021, Sun et al. 2024).

Angioedema, urticaria, and anaphylaxis

In a study involving 10 patients (5 children and 5 adults), a 2-year-old female child with a confirmed catfish allergy—demonstrated by a double-blind placebo-controlled food challenge (DBPCFC)—experienced symptoms of angioedema and generalized urticaria upon ingestion of catfish. Among the 5 adults, a 25-year-old female with a positive DBPCFC to catfish, cod, and snapper had previously experienced anaphylaxis upon ingesting these fish species (James et al. 1997).

In another study conducted on 5,162 patients with food allergies, 5 patients experienced allergic reactions after consuming catfish, all of whom reported skin symptoms such as angioedema, urticaria, flushing, and pruritus (Khan et al. 2011).

Respiratory

A study conducted on 5,162 patients with food allergies found that, among the 5 patients experiencing allergic reactions after consuming catfish, only 1 developed respiratory symptoms such as cough, dyspnea, wheezing, chest tightness, and throat swelling (Khan et al. 2011).

Eye/Nasal

Eye and nasal symptoms—such as ocular pruritus, coryza, rhinorrhea, nasal congestion, nasal itching, and sneezing—were reported in 1 out of 5 patients who experienced allergic reactions to catfish in a study conducted on 5,162 patients with food allergies (Khan et al. 2011).

Atopic dermatitis

A study conducted on 10 patients (5 children and 5 adults) reported that a 2-year-old female child experienced AD after ingesting catfish. Her catfish allergy was confirmed by a DBPCFC (James et al. 1997).

Diagnostic Relevance

Diagnosis of fish allergies generally involves an assessment of medical history along with diagnostic tests such as specific IgE measurement and skin prick testing (SPT). In some cases, oral food challenge (ideally, double-blind placebo-controlled challenge) with the fish that has elicited the reaction is considered. Component-resolved diagnostics (CRD) is an emerging diagnostic technique that can help identify the specific culprit allergen and cross-reactivity patterns. At present, only a limited fish allergens (cod and carp parvalbumin) are currently available for CRD testing (Buyuktiryaki et al. 2021, Kalic et al. 2021).

In a study following the natural history of fish allergy it was found that it will resolve spontaneously by adolescence in a considerable proportion of children, particularly in cases with less severe reactions and a lower level of sensitization (Xepapadaki et al. 2021). Thus, diagnostic reassessment of fish allergic children, at regular intervals, depending on age, and patient's history, may be considered to identify possible development of spontaneous tolerance (Santos et al. 2023).

Prevention and Therapy

Prevention strategies

The management of fish allergies typically involves completely avoiding fish and foods that contain fish products due to the risk of severe allergic reactions. Therefore, accurate food labeling is essential to ensure the safety of affected individuals (Kalic et al. 2021).

Molecular Aspects    

Allergenic molecules

The major fish allergen, parvalbumin, is responsible for most IgE-mediated allergic reactions to fish. It remains stable during cooking and can also be present in steam. Parvalbumins have two isoforms: the non-allergenic α-parvalbumin, found in cartilaginous fish, and the allergic β-parvalbumin, present in bony fish (Mourad et al. 2015). As of August 2025, no allergens from channel catfish (I. punctatus) have been recognized by the WHO/IUIS Allergen Nomenclature Sub-Committee. However, the parvalbumin gene has been isolated and characterized from channel catfish (Kim 2003). A gel electrophoresis analysis conducted on extracts of catfish, cod, snapper, and tuna exhibited a major protein band of 12.5 kDa, corresponding to the molecular weight of parvalbumin (James et al. 1997). In another study, an indirect enzyme-linked immunosorbent assay identified positive immunoreactivity between parvalbumin from channel catfish and anti-frog parvalbumin monoclonal antibody (Gajewski et al. 2009).

For striped catfish (P. hypophthalmus), 10 allergens are listed and recognized by the WHO/IUIS allergen nomenclature subcommittee, including parvalbumin Pan h 1 (Ruethers et al. 2021).

Monoclonal IgG parvalbumin antibodies showed positive immunoreactivity between parvalbumin from channel catfish and Pangasius hypophthalmus (common name: Tra), and Pangasius bocourti (common name: Basa) (Gajewski et al. 2009). Thus, IgE-mediated cross-reactivity can be expected between channel catfish parvalbumin and Pan h 1 from Pangasius.

Biomarkers of severity

Parvalbumins, found in various fish species, are a major cause of fish allergies. They exhibit high cross-reactivity, leading to allergic reactions in individuals sensitized to one fish species when exposed to others (Mukherjee et al. 2023). As a result, parvalbumin is recognized as a marker allergen for clinical cross-reactions (Hilger et al. 2017).

Cross-reactivity

Cross-reactivity is commonly observed among parvalbumins of different fish species, especially those belonging to the same family or genus, as they share common IgE epitopes (Kalic et al. 2021). A study involving 249 children found that 88% of patients were cross-sensitized to parvalbumins from several fish species, including catfish, tilapia, tuna, herring, salmon, halibut, grass carp, cod, and grouper (Leung et al. 2024). An immunoblot inhibition study using cod fish extract and serum from a pediatric and an adult patient with fish allergy showed complete inhibition of IgE binding to a catfish protein of size 12.5 kDa—similar in size to cod parvalbumin (James et al. 1997).

Explained Results

Allergen information

Channel catfish (I. punctatus) is a commercially important species in the family Ictaluridae. Consumption of catfish can cause allergic reactions in sensitized individuals. The major fish allergen parvalbumin has been detected in channel catfish.

Clinical information

Clinical manifestations following exposure to fish allergens can range from mild symptoms such as local urticaria and oral allergy symptoms, to severe anaphylactic reactions.

Cross-reactivity

IgE-mediated cross-reactivity has been observed among several fish species, including catfish, tilapia, tuna, herring, salmon, halibut, grass carp, cod, and grouper.

Compiled by Turacoz.

Reviewed by Dr. Michael Spangfort, August 2025