Food allergy and allergy to Fish and shellfish
A food allergy is an abnormal immune response to food. When someone with a food allergy eats the food they are allergic to, their immune system overreacts and produces antibodies called immunoglobulin E (IgE). These antibodies trigger the release of histamine and other chemicals into the bloodstream, which causes the allergy symptoms.
Food allergies can be mild or severe, and the symptoms can vary from person to person. Some common symptoms of a food allergy include:
- Skin reactions, such as hives, itching, and eczema
- Swelling of the lips, tongue, face, or throat
- Wheezing, difficulty breathing, or shortness of breath
- Stomach pain, nausea, vomiting, or diarrhea
- Dizziness or fainting
In some cases, a food allergy can cause a severe reaction called anaphylaxis. Anaphylaxis is a life-threatening condition that requires immediate medical attention.
Food allergies are most common in children, but they can develop at any age. The most common food allergens are milk, eggs, peanuts, tree nuts, soy, wheat, fish, and shellfish.
If you think you or your child may have a food allergy, it is important to see a doctor for diagnosis and treatment. There is no cure for food allergies, but there are ways to manage them. The most important thing is to avoid the food that you or your child is allergic to. There are also medications that can help to relieve allergy symptoms.
Allergy to fish
The main fish allergens are substances called parvalbumins (PA). Parvalbumins are a group of proteins found only in the muscles of fish and amphibians. PAs do not occur in mollusks, crustaceans, nor in higher vertebrates (reptiles, birds and mammals). The role of PA is to regulate the passage of Ca2+ in cells. Minor fish allergens are Ag-17-cod (protamine sulfate) and surimi 63 kDa protein.
Tab. I: PA content in raw meat of selected fish. Individual fish species are sorted in the group according to decreasing PA content.
Name | Average PA content [mg/g]* |
Wolffish, Carp, Eel, Herring, Perch | >2.5 |
Cod, Salmon, Tilapia, Frogs, Trout | 1-2.5 |
Mackerel | 0.3-0.7 |
Anchovies, Tuna | <0.05 |
*The PA content is 20 to 60% lower in cooked or commercial meat.
Problematic properties of PA
resistant to heat processing and proteolytic digestive enzymes, potential risk of secondary food contamination caused by water vapor transfer of allergens.
A typical representative of PA
Gad c 1 protein contained in cod (M = 12.328 kDa, 113 amino acids residues, pI = 4.75), from which it was also first isolated. There is approximately 34% amino acid sequence homology with the structurally similar protein from carp, hake and pike. Gad c 1 contains at least five IgE**-binding factors.
**IgE (immunoglobulin E) is a type of antibody found in human blood serum, whose function is in the area of anti-parasitic immunity. Increased levels of IgE are associated with frequent hypersensitivity such as allergic asthma, allergic inflammation of the nasal mucosa, atopy (a type of allergic reaction mediated by IgE and the release of certain substances such as histamine, which leads to narrowing of blood vessels and bronchi, the formation of swelling, etc.) and also parasitic infections.
Manifestations of allergy
On the skin (even by contact with food – hives, rash, swelling), digestive problems (abdominal pain, especially in the pelvic area, diarrhoea, nausea, vomiting), respiratory problems (shortness of breath, stuffy nose), up to anaphylactic shock , which can lead to cardiac arrest and sudden death (failure of circulation or inability to breathe).
Help
Epinephrine – adrenaline injection and call for help.
Incidence of allergy in the population
In the Czech Republic approximately 0.5% of the population, while 40% of people suffering from this allergy tolerate at least one type of fish and 60% have food allergies to all types of fish.
Allergy persistence
In most cases, food allergy to fish is a permanent disease and the disease does not go away in patients in life.
Crustacean allergens
The most common crustaceans are shrimps, crabs, lobsters and shrimps. The main allergen of molluscs and crustaceans is tropomyosin, a group of proteins showing considerable structural homology among themselves in amino acid sequence. The most studied shellfish allergens are summarized in Table II.
Tab. II: The most studied shellfish allergens.
Major allergens | Minor allergen |
antigen I and II | tRNA (transfer RNA) |
SA-I | |
SA-II | |
Pen a 1 | |
Pen i 1 | |
Met e 1 |
Antigen I is a heat-labile protein found in raw shrimp and mussels (raw shell) with a molar mass of 45 kDa. Antigen II is a heat-stable glycoprotein with a mass of 38 kDa composed of 341 AMK residues and 4% carbohydrates.