If you buy through links on this page, we may earn a small commission. Although most major food allergies begin in childhood , one allergy in particular stands apart: shellfish. Along with fish, shellfish allergies are the most common adult-onset food allergies. There are two kinds of shellfish, crustaceans and mollusks. Most people who are allergic to one type of shellfish are also allergic to the other type.
However, doctors usually recommend that people with shellfish allergies avoid all varieties to be safe. A shellfish allergy is different from other allergies in other ways, as well.
For example, allergic reactions to shellfish are unpredictable, sometimes occurring long after a person has consumed the allergen and has shown no other symptoms. Allergic reactions to shellfish also often become more severe with each exposure. Antibodies trigger the release of chemicals such as histamines to attack the tropomyosin. The histamine release leads to a number of symptoms that can range from mild to life-threatening.
Symptoms of shellfish allergies tend to lean toward the severe. It can take some time for symptoms to present after eating shellfish, but most develop within minutes. Symptoms of a shellfish allergy may include:. A severe, life-threatening allergic reaction known as anaphylaxis may occur in the most serious cases.
An anaphylactic reaction requires immediate medical attention. Symptoms of anaphylaxis include:. The best treatment is to avoid foods such as shrimp, lobster, crab, and other crustaceans.
Finned fish are not related to shellfish, but cross-contamination is common. You may want to avoid seafood altogether if your shellfish allergy is severe. Many doctors also recommend that people with shellfish allergies carry epinephrine EpiPen , Auvi-Q , or Adrenaclick for self-administration in case you accidentally ingest any.
Epinephrine adrenalin is the first-line treatment for anaphylaxis. Additionally, people with shellfish allergies do not necessarily have to eat it to have a reaction. They may react when other foods come in contact with shellfish during the food preparation process. Reactions often affect multiple parts of the body—skin, respiratory tract, gastrointestinal tract, and the cardiovascular system. The skin-prick test will be performed in the allergist office and you can expect to have results fairly quickly—often within 15 minutes.
A small spot on your forearm or upper back will be pricked with a sterile tooth pick-like stylet and drop of liquid containing the allergen will be introduced at prick site. If you have a positive reaction to shellfish you will immediately develop a small raised hive where your skin was pricked.
For blood tests, a blood sample is taken and tested for the presence of Immunoglobulin E IgE antibodies—these antibodies are produced by your body in response to a particular allergen in this case shellfish and results are typically available in a week to two weeks. The best and only definitive treatment for shellfish allergies is strict avoidance and elimination of any foods containing shellfish from your diet.
Additionally, anyone with shellfish allergies must check ingredient labels on packaged and prepared foods. You should also avoid seafood restaurants, even if you order non-shellfish containing meals it may be impossible for the kitchen to not cross-contaminate your meal. The absence of shellfish terms does not mean the food is safe for you though. If in doubt, contact the manufacturer and avoid the food unless you are certain it is free of allergens.
While people allergic to shellfish are sensitive to protein and not shell constituents, tests to exclude protein contamination are not routinely performed and there is little proof of safety in people with shellfish allergy, although challenge studies of small numbers of patients have demonstrated tolerance. This risk is considered to be very low. Your doctor will normally ask a series of questions that may help to narrow down the list of likely causes of allergy such as foods or medicines consumed that day, or exposure to stinging insects.
This approach will also help to exclude conditions that can sometimes be confused with food allergy. Skin or blood allergen specific IgE allergy tests help confirm or exclude potential triggers.
While the results of allergy testing are a guide to whether the person is allergic, results are not a reliable guide to whether the reaction will be mild or severe. It is also important to be aware that it may not be possible to test for all seafood species using commercial skin prick or blood allergy testing, since these are not available for all seafood species.
For this reason, some allergy clinics will recommend that you bring samples of fresh food for testing. Most of the time, children with food allergy do not have parents with food allergy. However, if a family has one child with food allergy, their brothers and sisters are at a slightly higher risk of having food allergy themselves, although that risk is still relatively low.
Some parents want to have their other children screened for food allergy. If the test is negative, that may be reassuring, but does not mean that the other child will never develop an allergy later. If their screening test is positive, it is not always clear whether it definitely represents allergy, or whether the sensitisation detected by the test is clinically irrelevant. The term "false positive" is sometimes used to describe this. It is important to know that a positive skin or blood allergy test means that the body's immune system has produced a response to a food, but sometimes these are false positives.
In other words, the test may be positive yet the person can actually eat the food without a problem. For that reason, it is important to eventually confirm the significance of a positive allergy test in some circumstances with a deliberate supervised food challenge.
In a child with a positive test of uncertain meaning, this is often done around school age under medical supervision. Examples include cytotoxic food testing, Vega testing, kinesiology, iridology, pulse testing, Alcat testing, allergy elimination and Rinkel's intradermal skin testing. These are unreliable, have no scientific basis and have no useful role in the assessment of allergy.
So if you suspect a possible food allergy, have the suspicion confirmed with a reliable test. Some conditions caused by adverse reactions to seafood can resemble allergic reactions.
These include:. This is an allergy like reaction that occurs after eating fish that have been improperly refrigerated after capture. Bacteria in and on the fish break down proteins into histamine, one of the major mediators of allergic reactions. Fish with a high content of red meat, which turns brown upon cooking are commonly involved such as mackerel, tuna, king fish, herring, sardines, marlin, anchovies and bluefish.
Affected fish often have a metallic or peppery taste. Symptoms usually commence within 30 minutes of eating, and include flushing, itch, hives urticaria , nausea, vomiting, stomach cramps, dizziness, palpitations and headache.
Severe episodes may result in wheezing and dizziness or a drop in blood pressure. Mild symptoms may be treated with antihistamines. If severe symptoms are experience, then urgent medical assistance should be sought. Treatment usually involves taking antihistamines although in a hospital setting, adrenaline may also be given. Scombroid poisoning can be different by the pattern of symptoms and the absence of reactions with skin or blood allergy testing. This is a nematode worm that is a fish parasite.
It is found in most parts of the world and also in Australia [see reference below]. Cooking at temperatures above 60 o C or storage in industrial freezers for 2 days is required to kill the parasite. Fish that has been left for 48 hours or longer since being frozen should be discarded. Anasakis can cause two major problems in humans:. Even people who have eaten shellfish in the past can develop an allergy.
Some people outgrow certain food allergies over time, but those with shellfish allergies usually have the allergy for the rest of their lives. When someone is allergic to shellfish, the body's immune system , which normally fights infections, overreacts to proteins in the shellfish. Every time the person eats or, in some cases, handles or breathes in shellfish, the body thinks these proteins are harmful invaders and releases chemicals like histamine.
This can cause symptoms such as:. Allergic reactions to shellfish can differ. Sometimes the same person can react differently at different times. Some reactions can be very mild and involve only one system of the body, like hives on the skin.
Other reactions can be more severe and involve more than one part of the body. Shellfish allergy can cause a severe reaction called anaphylaxis , even if a previous reaction was mild. Anaphylaxis might start with some of the same symptoms as a less severe reaction, but can quickly get worse. The person may have trouble breathing or pass out. More than one part of the body might be involved. If it isn't treated, anaphylaxis can be life-threatening.
If your child has a shellfish allergy or any kind of serious food allergy , the doctor will want him or her to carry an epinephrine auto-injector in case of an emergency.
An epinephrine auto-injector is a prescription medicine that comes in a small, easy-to-carry container. It's easy to use. Your doctor will show you how. Kids who are old enough can be taught how to give themselves the injection.
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