Understanding fish and shellfish allergy in babies and children…
Can babies eat fish and shellfish?
Yes- absolutely! Seafood can be an incredibly nutritious part of your baby’s diet- they are rich in protein, iron, iodine and essential omega-3 fats
What about allergy to fish? Or shellfish allergy in children?
Seafood allergies are among the most common food allergies in children and can be categorised into:
Fish: e.g. cod, salmon, tuna
Shellfish, which includes
Crustaceans: e.g. prawns, shrimp, crab, lobster
Molluscs: e.g. mussels, clams, squid
Can my child be allergic to one fish type and not another?
Yes! It’s possible for a child to be allergic to one type of seafood and not others.
Seafood allergy, how common is it?
Seafood is increasingly recognised as a common food allergen, with shellfish-particularly crustaceans like shrimp and crab- being among the most frequently reported triggers. Globally, it’s estimated that around 2.5% of the population experience adverse reactions to seafood, with crustaceans causing more allergic reactions than molluscs.
A large telephone survey conducted in the United States found that 2–3% of participants believed they had a seafood allergy, including 2.2% to shellfish and 0.6% to fish.
Interestingly, shellfish allergy was far less common in children (0.5%) than in adults (2.5%), and the most frequently implicated shellfish were shrimp, crab, and lobster, followed by clam, oyster, and mussels.
In the UK, several cohort studies have explored the incidence of fish and shellfish allergies in children. One of the most comprehensive is the Isle of Wight Birth Cohort, which tracked allergy development from birth to age 18. It found that fish allergy was consistently present in 0.2% of children across all age groups, while shellfish allergy began to appear at ages 10 and 18, also at a rate of 0.2% (Isle of Wight study). The study concluded that shellfish allergy is more likely to develop later in childhood or adolescence, often persisting into adulthood.
⚠️ What are the symptoms of fish allergy in children?
Allergic reactions to fish and shellfish can vary in babies and children but often include:
Skin reactions: hives, itching, or eczema
Gastrointestinal symptoms: nausea, vomiting, diarrhea
Respiratory issues: wheezing, nasal congestion, or trouble breathing
Anaphylaxis: a severe, potentially life-threatening reaction that requires immediate medical attention
Symptoms of IgE seafood allergy typically appear within minutes to two hours after consuming the allergen. But reactions can also be non-IgE and result in more delayed reactions occurring hours of even days after exposure.
IgE-mediated allergy reactions to fish or shellfish occur within about two hours after ingestion of the shellfish and range from urticaria, angioedema, nausea, and vomiting to respiratory signs and symptoms such as bronchospasm, laryngeal oedema, and anaphylaxis.
Non-IgE-mediated reactions to fish: include syndromes such as Food Protein-Induced Enterocolitis Syndrome (FPIES) and Food Protein-Induced Allergic Proctocolitis (FPIAP), of which fish is a common cause and also eosinophilic esophagitis (EoE). In the management of EoE, a six-food elimination diet is often recommended and includes the elimination of fish/shellfish along with milk, egg, wheat, nuts, and soy, although some specialists recommend a four-food elimination diet initially and allow taking nuts and fish- this depends on the individual baby or child
Do children outgrow seafood allergies?
Unlike some food allergies (e.g. milk or egg), seafood allergies are less likely to be outgrown. Many individuals retain these allergies into adulthood. However, each case is unique, and some children may develop tolerance over time
Tips for introducing seafood, fish and shellfish to babies
Introducing seafood to your baby’s diet can be done safely with the following guidelines:
Start small: Seafood are a common allergen food. I wouldn’t usually recommend giving them as a first food, incase of a reaction. Once your baby is tolerating a few non-allergenic foods, offer a small amount of fish on day 1- like 1/2 teaspoon- and gradually build up the amount if no reaction occurs
Introduce seafood at lunch: Offer new allergens earlier in the day when support is available, and ideally not right before a nap or at bedtime. It might also sound silly but avoid giving within 2 hours of sunset or lights being dimmed in the house, so you can easily see your child’s skin if there is a reaction
Monitor for reactions: After introducing seafood, watch for any signs of allergy for at least 2 hours
Introduce one new potentially allergenic food at a time: Leave at least a whole day in between, but ideally 72 hours, so that if there is a delayed reaction, it’s easier for you to pinpoint the cause
Avoid raw or undercooked seafood: Always cook fish and other seafood thoroughly!
Consult with a dietitian: If your baby has moderate/severe eczema or other food allergies, seek advice before introducing seafood.
Mercury in fish and what it means for babies
Mercury is a naturally occurring heavy metal found in varying levels in fish.
In high amounts, it can affect a baby’s developing brain and nervous system, so it’s important to choose lower-mercury fish when introducing seafood to your baby.
Lower-mercury fish include options like salmon, cod, haddock, pollock, sardines, trout, hake, canned tuna, mackerel and sole.
Serving a variety of lower-mercury fish 1–2 times per week is a great way to support your baby’s growth and brain development
Try to avoid (or limit) high-mercury fish such as shark, swordfish, king mackerel, fresh tuna and tilefish, especially during the first years of life.
The nutritional benefits of fish likely outweigh the risks from mercury exposure as long as you moderate your consumption of mercury-containing fish and limit/avoid those with high levels
The NHS advises, in response to ‘Should children and babies over 6 months eat fish?’
Children under the age of 16 should avoid eating any shark, swordfish or marlin. This is because the levels of mercury in these fish can affect a child's nervous system.
Avoid giving raw shellfish to babies and children to reduce their risk of getting food poisoning.
You can give boys up to 4 portions of oily fish a week, but it is best to give girls no more than 2 portions a week. This is because the levels of pollutants that oily fish contain can build up in the body and may harm an unborn baby during a future pregnancy
Oily fish to limit to 2 portions per week, include:
herring (bloater, kipper and hilsa are types of herring)
pilchards
salmon
sardines
sprats
trout
mackerel
The following white fish may contain similar levels of certain pollutants as oily fish, and should be included in the limits:
sea bream
sea bass
turbot
halibut
rock salmon (also known as dogfish, flake, huss, rigg or rock eel)
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More information
For more detailed information, you can refer to the following resources:
Shellfish and fish allergy in children
IgE-Mediated Shellfish Allergy in Children - PMC
IgE-Mediated Fish Allergy in Children - PMC
Seafood allergy prevelance studies
Sicherer, S. H., & Sampson, H. A. (2012). Food allergy: epidemiology, pathogenesis, diagnosis, and treatment. Journal of Allergy and Clinical Immunology, 129(5), 1112–1120.
Venkataraman, D., Erlewyn-Lajeunesse, M., Kurukulaaratchy, R. J., et al. (2018). Prevalence and longitudinal trends of food allergy during childhood and adolescence: Results of the Isle of Wight Birth Cohort study. Clinical & Experimental Allergy, 48(4), 394–402. https://doi.org/10.1111/cea.13088
Mercury levels in fish
Brodziak-Dopierała B, Fischer A. Analysis of the Mercury Content in Fish for Human Consumption in Poland. Toxics. 2023 Aug 21;11(8):717. doi: 10.3390/toxics11080717. PMID: 37624222; PMCID: PMC10457943. https://pubmed.ncbi.nlm.nih.gov/37624222/
Note: The suggestions I offer are for information only and do not a substitute for child-specific advice from a professional.