Shellfish allergy is an immune system reaction to proteins found in certain marine animals, such as crustaceans (shrimp, crab, lobster) and mollusks (clams, oysters, scallops). Reactions can range from mild discomfort to severe, life-threatening conditions. Professional medical diagnosis and accurate testing are important for managing this allergy.
Symptoms Indicating a Need for Testing
Symptoms of shellfish allergy often appear rapidly, within minutes to an hour after consuming or contacting shellfish. Mild indicators include skin reactions like hives, itching, or swelling of the lips, face, or throat. Digestive issues may also arise, such as abdominal pain, nausea, vomiting, or diarrhea.
More concerning symptoms involve the respiratory system, including difficulty breathing, wheezing, coughing, or a tight feeling in the chest. In severe cases, an allergic reaction can escalate to anaphylaxis, characterized by dizziness, a weak pulse, fainting, or pale skin. Prompt medical evaluation and testing are needed if these symptoms occur after shellfish exposure.
Common Shellfish Allergy Tests
Medical professionals use several methods to diagnose shellfish allergies, starting with a detailed review of an individual’s medical history. These diagnostic tools aim to identify the body’s immune response to shellfish proteins.
The Skin Prick Test (SPT) is a common initial diagnostic approach. During this procedure, a small amount of liquid containing shellfish protein extracts is pricked onto the skin, usually on the forearm or back. A positive reaction, appearing within 15 to 20 minutes, is a raised, red, itchy bump resembling a mosquito bite. While SPT can suggest sensitization, meaning the body has produced antibodies to shellfish, it does not always confirm a clinical allergy.
A Blood Test, also known as a specific IgE blood test, measures immunoglobulin E (IgE) antibodies in the blood. This test offers advantages such as posing no risk of an allergic reaction and not being affected by antihistamine medications. However, like SPT, a positive blood test indicates sensitization and must be interpreted with a patient’s clinical history to confirm an allergy.
The Oral Food Challenge (OFC) is the most definitive method for diagnosing a shellfish allergy. This test is conducted under strict medical supervision in a clinical setting, where the patient consumes gradually increasing amounts of the suspected shellfish allergen. Medical staff closely monitor for any allergic reactions throughout the challenge. OFCs are performed when other tests are inconclusive or to determine if an allergy has been outgrown. At-home allergy tests are not reliable and should not be used for diagnosis, as they can provide inaccurate or misleading results.
Understanding Your Diagnosis and Management
A confirmed shellfish allergy diagnosis means completely avoiding shellfish to prevent allergic reactions. This involves careful attention to food labels, as federal regulations require manufacturers to list common allergens like shellfish. Awareness of potential cross-contamination, especially when dining out, is also important, as shellfish proteins can inadvertently transfer to other foods.
For individuals at risk of severe reactions, carrying an epinephrine auto-injector, such as an EpiPen, is a safety measure. Epinephrine is the first-line treatment for anaphylaxis, a severe, life-threatening allergic reaction. Patients are instructed on how and when to use this device, and should always seek emergency medical care after its administration. Ongoing management of a shellfish allergy involves regular consultation with an allergist, who can provide guidance on avoidance strategies and emergency preparedness.