Fish allergy in babies

Fish allergy: the basics

Fish allergy is an allergy to finned fish, such as salmon, cod, tuna or halibut. It happens when the immune system overreacts to proteins in fish. It’s less common than some other food allergies, but ACAAI says it’s a frequent cause of anaphylaxis, and the NHS lists fish among the foods that can cause it.

Unlike milk, egg and soy allergies, which many children outgrow, fish allergy usually lasts for life (ACAAI). ACAAI also notes that, unlike most food allergies, fish allergy sometimes doesn’t show up until adulthood.

Fish and shellfish are separate allergies

Shellfish (shrimp, crab, lobster, clams, mussels) are a different group of foods. ACAAI says a fish allergy doesn’t mean a shellfish allergy, and the reverse is also true: there appears to be no link between the two. A child can be allergic to both, the same way a child can be allergic to egg and peanut. If your baby reacts to one, ask your allergist before offering the other. See shellfish allergy.

Introducing fish

Fish can go in with your baby’s other first foods, from around 6 months. The NHS lists fish among the foods that can trigger allergy and can be introduced from around 6 months, one at a time, so you can spot any reaction. The AAP lists fish with egg, peanut, dairy and the other allergens to offer once your baby has managed a few lower-risk first foods.

Always serve fish fully cooked. The FDA says children should avoid raw or undercooked fish, and that fish is cooked when it reaches 145°F (63°C), or when the flesh separates easily with a fork. Good first forms:

• baked or poached salmon or cod, flaked into large soft pieces
• flaked fish mashed into potato and shaped into soft, finger-sized fish cakes
• flaked fish stirred into a sauce, rice or a mash your baby already eats

Check carefully for bones. The CDC says to remove all skin and bones from fish before cooking. See fish for babies for which fish are low in mercury and how much to offer.

Offer the first taste on a day your baby is well, at home, when you can watch them for a couple of hours afterward. Start with a small amount, and if there’s no reaction, build up over the next few servings. Then keep fish in your baby’s diet: see keeping allergens in the diet.

Talk to your doctor first if your baby has severe eczema, an egg allergy, or has already reacted to a food (AAP). Ask how and when to introduce fish and the other allergens, not about putting them off.

Signs of fish allergy

Reactions usually start within minutes of eating, but can take up to 2 hours (NHS).

Mild to moderate (ACAAI, NHS):

• hives or a red, itchy rash
• mild puffiness of the face or around the eyes
• vomiting once, tummy pain or diarrhea
• sneezing, or a stuffy or runny nose

If it’s only one of these, stop offering fish, stay with your baby and watch them closely for the next couple of hours, and call your pediatrician before you offer any fish again. If signs show up in more than one part of the body at once, treat it as anaphylaxis (below).

Signs of anaphylaxis are trouble breathing, wheezing or a cough that won’t stop, swelling of the tongue or throat, lips or mouth that suddenly swell, a hoarse cry, turning pale or floppy, becoming very sleepy or unresponsive, or signs in more than one part of the body at once. If you see any of these and your baby has an epinephrine (adrenaline) auto-injector, use it right away, then call for an ambulance. Call 911.Call 999.Call your local emergency number (such as 112 in Europe or 000 in Australia). If you don’t have an auto-injector, call straight away. Keep your baby lying down, never standing or walking (on their side if they’re vomiting, head and shoulders a little raised if breathing is hard), and go to hospital even if they seem better. See signs of anaphylaxis.

Two things that can look like fish allergy

FPIES. Fish is one of the foods ACAAI lists as a common trigger of FPIES, a delayed allergy that affects the gut. Instead of hives, a baby vomits again and again, starting a few hours after eating, and may turn pale or floppy. The usual allergy tests are typically negative. If your baby vomits once or twice a few hours after fish and is alert and like themselves, call your pediatrician or GP. Call 911 or go to the emergency room if your baby is vomiting again and again, or is pale, floppy, very sleepy or hard to wake.Call 999 or go to A&E if your baby is vomiting again and again, or is pale, floppy, very sleepy or hard to wake.Call your local emergency number (such as 112 in Europe or 000 in Australia) or go to the emergency department if your baby is vomiting again and again, or is pale, floppy, very sleepy or hard to wake. See FPIES.

Scombroid poisoning. Fish such as tuna, mackerel, sardines and anchovies that weren’t kept cold enough after being caught can build up a toxin that causes flushing, itching, headache and diarrhea within minutes to an hour. The CDC says it often looks like an allergic reaction, and cooking or freezing doesn’t prevent it. You can’t tell the two apart at home, and you don’t need to: if your baby has any of the signs of anaphylaxis above, give epinephrine (adrenaline) if your baby has an auto-injector, then call for an ambulance. Call 911.Call 999.Call your local emergency number (such as 112 in Europe or 000 in Australia). Otherwise, stop the fish, call your pediatrician or GP, and say what fish your baby ate.

How fish allergy is diagnosed

Your doctor or an allergist will ask what happened and may arrange a skin prick test or a blood test for IgE to the fish your baby ate. If the results aren’t clear, the allergist may suggest an oral food challenge: small amounts of fish given under medical supervision, in an office with emergency medicine on hand (ACAAI). Don’t try a challenge at home.

Living with fish allergy

Avoid all fish until your allergist says otherwise. ACAAI says doctors usually advise people allergic to one kind of fish to avoid all kinds. Some can eat other fish safely, but that’s something your allergist decides with testing. Don’t change your child’s diet on your own.

Read labels every time:

• US labels must name the species of fish, such as “cod” or “salmon”, in the ingredients or a “Contains” statement (FDA).
• UK labels must emphasize fish in the ingredients list, for example in bold (GOV.UK).
• Where fish hides. ACAAI lists Worcestershire sauce, Caesar dressing, imitation crab (surimi, usually made from pollock) and fish-based stocks in many Asian dishes.
• Fish gelatin and fish oil. Some people react to fish gelatin, and ACAAI says to ask your allergist before giving any fish oil supplement.
• Cross-contact. ACAAI notes that fish proteins can get into other food during cooking and into the air where fish is cooked, so tell anyone who cooks for your child.

Fish gives protein, iodine and healthy fats. If your child can’t eat it, an allergy dietitian can help you plan other sources. Keep introducing the other common allergens as your doctor advises.

When to see a doctor

Call your pediatrician or GP if:

• your baby has had any reaction to fish, even a mild one
• your baby has vomited once or twice a few hours after eating fish and seems alert and like themselves
• your child has a fish allergy and you want to know about other fish, shellfish or other allergens

Don’t cut fish or other major foods out on your own: the NHS says to talk to your health visitor or GP, who may refer you to a dietitian.

Where US and UK advice differs

• How labels show it. US labels must name the type of fish (FDA). UK labels list fish as one of 14 allergens, emphasized in the ingredients list, and loose food sellers must tell you if you ask (GOV.UK).
• Who should check first. The NHS asks you to talk to your GP or health visitor before introducing allergens if your baby has eczema or a food allergy, or there’s a family history of food allergies, eczema, asthma or hay fever. US guidance singles out severe eczema and egg or other food allergy.

For the other allergens, see how to introduce allergens and the safe first form of each one.