Symptoms, diagnosis, treatment and adaptation to fish allergy
A fish allergy, as opposed to a shellfish allergy, is an allergy in which your immune system reacts abnormally to a finned fish such as tuna, halibut, or salmon. This is a somewhat less common form of food allergy, affecting women more than men and adults more than children.
Fish allergies often develop in early childhood but, unlike a milk or egg allergy, usually persist well beyond school age.Inasmuch asSymptoms can range from mild to severe and may include skin rashes, respiratory symptoms, gastrointestinal distress, and anaphylaxis (which requires emergency attention).
The allergy is more common in areas where fish is a predominant part of the local diet, such as Scandinavia and parts of Asia. An allergy can not only be triggered by eating fish, but also by touching fish or consuming foods containing fish by-products.
Fish Allergy Symptoms
Fish allergy symptoms are similar to other food allergies and most occur within an hour of eating. They understand:
- Urticaria (hives) or rash
- Generalized itching
- Stuffy nose and sneezing (allergic rhinitis)
- Difficulty breathing (asthma)
- Indigestion and stomach pain
- belching, bloating, or flatulence
- Nausea or vomiting
Symptoms can also develop from simply inhaling cooked fish or coming into contact with surfaces or utensils used to prepare fish. In some cases, a skin reaction called contact dermatitis can develop from simply touching fish or fish residue.
In some people, a fish allergy can become severe and lead to the rapid development of anaphylaxis. This dangerous whole-body reaction is characterized by a generalized rash, swelling of the face and tongue, wheezing, shortness of breath, rapid heart rate, delirium, and a feeling of impending doom.
If not treated immediately with an injection of epinephrine and other emergency interventions, anaphylaxis can lead to shock, coma, heart or respiratory failure, and even death.
Allergies are caused by an abnormal immune response to an otherwise harmless allergy trigger, known as an allergen. When this happens, the immune system releases a substance known as immunoglobulin E (IgE), which causes mast cells and other blood cells to break open and release histamine into the bloodstream.
The normal role of histamine is to dilate blood vessels so that larger immune cells can gain access to the site of injury or infection. In the absence of injury or infection, histamines can trigger skin, respiratory, and gastrointestinal symptoms that we recognize as allergic reactions.
The main allergen responsible for a fish allergy is a protein called parvalbumin.Inasmuch asParvalbumins vary little between different species of fish, which means an allergy to one fish will usually lead to an allergy to other fish (a condition known as polysensitization).
Parvalbumins are extremely heat resistant and do not break down easily even after hours of cooking. As such, you can be just as sensitive to a piece of baked salmon as you are to raw sashimi.
Interestingly, although you can be allergic to different types of fish, a fish allergy does not predispose you to a shellfish allergy. A shellfish allergy involves an entirely different allergen called tropomyosin, which is found in crustaceans and molluscs.Inasmuch asInasmuch as
Fish associated with an allergy
Among the more than 20,000 known species of fish, there are several for which the risk of allergy is particularly high. According to a study published in the Frontiers of Immunitythey understand:Inasmuch asInasmuch as
- sea bass
Beyond the fish itself, fish or fish by-products are often used to make popular foods or condiments such as Worcestershire sauce, Caesar dressing, caponata (savory Sicilian eggplant), tarama and nuoc cham sauce.
Fish gelatin, derived from the bones and cartilage of fish, is often used as a setting agent in pepperoni, hot dogs, and other types of processed meats. Similarly, fishmeal is commonly used in some organic fertilizers.
A fish allergy can often be recognized by the onset of symptoms shortly after eating or being exposed to fish. To confirm that fish is the cause, an allergist may recommend two minimally invasive tests:Inasmuch asInasmuch as
- Skin tests involve the introduction of a small amount of a suspected allergen under your skin. If you are allergic to any of the many test samples, you will develop an inflamed bump (called a papule) within 15 to 60 minutes.
- Blood antibody tests are used to check for the presence of an immune protein called anti-parvalbumin antibody, which your body produces in response to a fish allergen.
If the tests are inconclusive, your allergist may recommend a oral food challenge.Inasmuch asThis is a procedure in which you eat a small amount of fish to see if you have a reaction.
Because the response to an oral food challenge can be severe, it is only performed in the presence and under the direction of a medical professional who can provide emergency treatment if necessary.
An oral food challenge should never be performed as a home experiment.
To be sure that fish is the source of your symptoms and not another condition, your healthcare provider may want to explore other possible causes. One such example is scrombroiosis, a type of food poisoning in which high levels of histamine are produced when a fish begins to spoil.
Other reactions may be caused by naturally occurring fish toxins which can cause poisoning in humans. Ciguatera, found in fish such as grouper, mackerel and snapper, is the most commonly reported fish toxin disease worldwide. It causes gastrointestinal, neurological and cardiovascular symptoms.
Less commonly, some people may experience cross-reactivity with chicken and fish, in which a true allergy to chicken parvalbumins can sometimes trigger a cross-reactivity with fish.
Since parvalbumins are found in varying degrees in different species of fish, you might be well served to exclude all fish from your diet if you are allergic. This includes any sauces, condiments or prepared foods containing fish or fish by-products.
Fish is one of eight allergens that must appear on all food ingredient labels under the Food Allergen Labeling and Consumer Protection Act 2004.Inasmuch asBy law, the manufacturer must identify the type of fish used and ensure that it is clearly stated in easy-to-understand language.
If your allergy symptoms are mild, you can often treat them with an over-the-counter oral antihistamine. If you are at risk of a severe reaction, you may be advised to carry a pre-filled single-use epinephrine injector, such as an EpiPen, with you to inject into your thigh in case of an emergency.Inasmuch asInasmuch as
Unlike other forms of allergies, food allergies cannot be treated with allergy shots (immunotherapy).
Although a fish allergy may be less common than a shellfish or tree nut allergy, it can be just as serious. To that end, you should take steps to protect yourself if you have been diagnosed with a fish allergy.
Some of the most useful tips:Inasmuch asInasmuch as
- Always read product labels. If you’re not sure if an ingredient on a label is fish, look it up on your smartphone.
- Let someone else do the fish shopping. Even in the cleanest seafood departments, surfaces, containers and packaging are susceptible to exposure to fish residue.
- Avoid fish restaurants. Even if you choose beef, fryers and griddles will likely have been used to cook the fish. There are simply too many opportunities for cross-contamination to take the risk.
- Be careful in Asian restaurants. Many traditional dishes, including spring rolls and curries, regularly combine meat and seafood. Many soups are also prepared with fish-based broths or contain bonito flakes (dried fermented tuna). If you don’t know what ingredient is on a menu, ask.
A word from Verywell
While some allergies can be annoying, others can be downright life-threatening. If you have ever had anaphylaxis or are at risk, consider wearing an emergency medical bracelet outlining your condition, recommended treatments, and medications to avoid.
So if you are unconscious or unable to respond, the emergency medical team can take appropriate action without wasting valuable time.