Shellfish allergies are caused by two classes of foods- a) molluscs which include clams, mussels, squid, octopus, cuttlefish, scallops, conch, limpets and oysters and b) crustaceans which include shrimp, lobster, prawns, crayfish, lobster, sea urchins and crabs.
If your doctor is able to recognize the exact type of shellfish that is responsible for your allergy, then you only need to remove that particular type. For the majority of shellfish allergy sufferers, however, this is not an option and all shellfish must be avoided.
These allergies are the one of eight most common allergies among American adults, and are more likely than most other allergies to show up for the first time in adults. In fact, an estimated two per cent of the population of the America suffers from shellfish allergies, second only to peanuts. Shellfish allergens are usually found in the flesh and are part of the muscle protein system, whilst allergens have also been found in the shells in foods such as shrimps.
Symptoms of shellfish allergy
Symptoms of shellfish allergy can show up in some minutes or may take a few hours. The most common symptoms of shellfish allergy include hives (or urticaria), swelling (angioedema), eczema, vomiting and nasal congestion. Hives can be quite itchy and can appear anywhere on the body, but are usually common around the stomach, back, thighs, backside, limbs, and face. Swelling commonly occurs on the lips, tongue and throat, hands and other parts of the body. Other symptoms of shellfish allergy include tingling in or around the mouth or throat, chest tightness, wheezing, trouble breathing, light-headedness, dizziness, fainting, nausea, vomiting, abdominal pain, and diarrhoea.
More-severe and even life-threatening reactions such as anaphylactic shock (presenting with constriction of airways, shock, sudden fall in blood pressure, rapid pulse, and loss of consciousness) can also occur. People have even been known to go into anaphylactic shock after breathing in airborne particles of shellfish or fish allergen in open fish markets. Loss of consciousness and death are the risks associated with these life-threatening symptoms.
Points to remember about shellfish allergy
Shellfish allergies pose a greater risk of severe reactions such as anaphylactic shock as compared to many other food allergies. Therefore, if you suffer from this allergy then you should strictly avoid shellfish and food containing shellfish to prevent this reaction.Please be informed that cooking does not destroy the allergens in fish and shellfish, and some individuals may be allergic to the cooked, but not raw shellfish.
It is important to bear in mind that cross-reactivity can occur between different types of shellfish. Tropomyosin is the protein that most commonly causes allergy problems and it is also found in dust mites and cockroaches. The immune system produces antibodies against the allergen, causing the release of histamines and other chemicals. Allergies can also be caused by the gelatin in the skin and bones of shellfish. There is some evidence of cross-reactivity between shellfish and some insects.
Prevention of shellfish allergy
You should avoid buying or consuming shellfish in case the same pair of pincers has been used to handle different types of fish and shellfish or if you presume that one type of fish or shellfish somehow got in contact with another.
Allergic patients can get affected by the steam from the cooking process as the allergy-causing proteins can be airborne. Such people should therefore be moved well away from the kitchen when another family member is cooking shellfish.
It is important to be careful with fried foods. Some restaurants use the same oil to fry shrimp, chicken, and French fries. Also, do not forget that imitation shellfish may still contain shellfish as many manufactures add shellfish for flavouring. So be vigilant to check the label before you use it.
Glucosamine is a food supplement for arthritic patients but people with shellfish allergy are advised against taking this supplement as it is expected to produce symptoms of this allergy. This happens rarely as glucosamine is made up of crustacean shells quite distinct from the flesh, which is the known site for the problem proteins responsible for producing shellfish allergy. However, if still concerned you can try vegetarian glucosamine.
Do not consume coral calcium if you're allergic to shellfish. Coral calcium, which is obtained from ocean coral reefs, can trigger allergic reactions in people suffering from shellfish allergies.
If you or your child suffer from shellfish allergy, it is important to keep your doctor informed about it no matter how mild the reaction may have been. Blood and skin tests can help confirm a shellfish allergy, so necessary steps can be taken to avoid future and potentially more-severe reactions.
Treatment of shellfish allergy
Medications such as antihistamines may reduce signs and symptoms of a shellfish allergy. Some relief can come to the shellfish allergy from the use of antihistamine tablets such as loratidine or diphenhydramine. Calamine lotion is also known to ease the itchiness associated with hives. Another way is to put ice on the hives as this shrinks the blood vessels and reduces inflammation. Milk of magnesia and peppermint tea are also helpful in reducing symptoms. For severe reactions like anaphylactic shock, an epinephrine injection and a trip to emergency could be required. It is always best to see a doctor while the symptoms are still present.
Skin and blood tests can be helpful in establishing a diagnosis for shellfish allergy. Skin prick tests are useful for testing allergies to each type of shellfish. A blood test determines how the immune system responds to shellfish protein by measuring antibody levels in the blood. If at risk of a severe reaction, an injectable epinephrine (such as an EpiPen) may be recommended to carry along with you at all times. Also, it is wise to wear an alert bracelet.