What is a Fish Allergy?

A fish allergy is an allergic reaction to finned fish such as tuna, halibut, and salmon. If you have a fish allergy and eat finned fish, proteins in the fish trigger your immune system to release histamine, a chemical that causes the symptoms of an allergic reaction. A fish allergy is a very common food allergy. Many people first experience a fish allergy as an adult, although children can have a fish allergy, too. A fish allergy to finned fish is not the same as a shellfish allergy, which is an allergy to shellfish such as crab, shrimp and lobster.  

Symptoms

An allergic reaction to fish can be mild or severe. The most common fish allergy symptoms are nausea, vomiting and hives. Hives are inflamed, raised bumps on the skin. Sometimes medical personnel refer to hives as a fish allergy rash. It is possible to have certain symptoms with one type of fish and a different set of symptoms with another kind of fish.

Common fish allergy symptoms include:

• Vomiting
• Nausea
• Hives
• Stomach pain
• Diarrhea
• Swelling
• Itchy eyes
• Watery eyes
• Swollen eyes
• Lightheadedness
• Coughing

Anaphylactic shock is a serious fish allergy reaction that requires urgent medical care. This symptom usually occurs immediately after exposure to fish. Wheezing, trouble swallowing, hoarseness, tightness in your throat, trouble breathing, and passing out are all signs of anaphylactic shock. Anaphylactic shock can be fatal.

Fish intolerance is not the same as a fish allergy. Unlike a fish allergy, a fish intolerance it typically temporary, non-life threatening, and symptoms only occur when you eat fish. Exposure to fish typically does not cause symptoms. Fish intolerance symptoms are usually gradual instead of immediate and may not occur at all unless you eat a lot of fish.

Causes

Fish allergies come from your immune system mistakenly reacting to certain proteins in fish as harmful substances or threats. Your immune system then releases histamine, a chemical that causes the symptoms of a fish allergy.

Allergic reactions have occurred in the following types of fish:

• Tuna
• Salmon
• Halibut
• Snapper
• Bass
• Flounder
• Perch
• Swordfish
• Grouper
• Tilapia
• Haddock
• Pollock
• Hake
• Trout
• Herring
• Mahi mahi
• Pike
• Scrod
• Sole

Fish allergies and shellfish allergies, while similar in name, are not related. Due to the many types of fish and fish allergies, this condition has also been called by numerous other names.

Common types of fish allergies:

• Salmon allergy
• Tuna allergy
• Cod allergy
• Catfish allergy
• White fish allergy
• Fish food allergy
• Raw fish allergy

You may also want to avoid fish products such as fish oil, fish sticks and fish gelatin, which is made of fish skin and bones. Fish can also show up in unexpected food items such as Worcestershire sauce, barbeque sauce, Cesar salad and Cesar salad dressing, bouillabaisse, imitation or artificial fish, imitation or artificial shellfish or caponata. Caponata is a Sicilian eggplant relish. Certain cuisines come with an increased risk of cross-contact with fish. These cuisines include African, Thai, Chinese, Vietnamese and Indonesian.

Diagnosis

To diagnosis a fish allergy, you doctor will perform a routine physical exam, review your family and medical history, and recommend additional tests to confirm a potential diagnosis. During these tests, your doctor will look for immunoglobulin E, which is an antibody that binds to certain allergens, and triggers the immune system to release histamine. Histamine causes the allergic reaction symptoms.

Fish allergy tests can include:

• Skin prick test – After pricking a small area of your skin, your doctor will expose that area to a sample of fish. If that area of your skin becomes inflamed with a rash or red bumps, then you may have a fish allergy.
• Blood test – Doctors will gauge how your immune system reacts to fish proteins. They will measure the amount of immunoglobulin E (IgE) antibodies in your blood, which can indicate a possible fish allergy.
• Oral food challenge – If the other tests do not definitely confirm a fish allergy diagnosis, your doctor may provide you with food items that contain fish to see if you have an allergic reaction.
• Food tracking and elimination diet – Your doctor may also ask you to track the food you eat every day, to eliminate foods, and to keep a diary of your symptoms. Your diary might include the time of day, type of fish or fish product, type of symptoms, severity of symptoms and more.

Management & Treatment

The best way to prevent a fish allergy is to avoid foods and food items that contain fish. While there is no fish allergy cure, there are several fish allergy treatments that can help you manage your condition.

Common prevention and management options include:

• Read food labels to avoid accidently exposing yourself to fish or food where fish is used as an ingredient.
• Inform restaurant servers, chefs, friends, family, and anyone else who may be preparing a meal for you about your fish allergy.
• Avoid seafood restaurants and fish markets where you may be unintentionally exposed to fish.
• Never consume food without knowing the ingredients or possible cross-contamination with fish.
• Always carry an emergency epinephrine auto-injector to address severe allergic reactions such as anaphylactic shock.

Allergic reactions to fish can sometimes be immediate, severe, and life-threatening. If you or a loved one experience any of the signs of a fish allergy, an allergy specialist at Baptist Health may be able to help.