Your doctor will ask about your symptoms and may perform a physical exam to find or rule out other medical problems. He or she may also recommend one or both of the following tests:
- Skin test. In this test, your skin is pricked and exposed to small amounts of the proteins found in shellfish. If you're allergic, you'll develop a raised bump (hive) at the test site on your skin.
- Blood test. Also called an allergen-specific IgE antibody test or radioallergosorbent (RAST) test, this test can measure your immune system's response to shellfish proteins by measuring the amount of certain antibodies, known as immunoglobulin E (IgE) antibodies, in your bloodstream.
A history of allergic reactions shortly after exposure to shellfish can be a sign of a shellfish allergy, but allergy testing is the only sure way to tell what's causing your symptoms and to rule out other possibilities, such as food poisoning. Medically supervised food challenges can be performed if any uncertainty remains about the diagnosis.
The only sure way to prevent an allergic reaction to shellfish is to avoid shellfish. But despite your best efforts, you may come into contact with shellfish.
Your doctor may instruct you to treat a mild allergic reaction to shellfish with medications such as antihistamines to reduce signs and symptoms, such as a rash and itchiness.
If you have a severe allergic reaction to shellfish (anaphylaxis), you'll likely need an emergency injection of epinephrine (adrenaline). If you're at risk of having a severe reaction, carry injectable epinephrine (EpiPen, Adrenaclick, others) with you at all times.
If you're at risk for anaphylaxis to shellfish, your doctor may instruct you to administer epinephrine even at the first sign of an allergic reaction. After you use epinephrine, seek emergency medical care, even if you've started to feel better.
Preparing for your appointment
You're likely to start by seeing your family doctor or a general practitioner. Or you may be referred immediately to an allergy specialist.
What you can do
Prepare for your appointment by writing down:
- Symptoms, including any that may seem unrelated to an allergy
- Family history of allergies and asthma, including specific types of allergies if you know them
- Medications, vitamins or supplements you're taking
- Questions to ask your doctor
Questions related to shellfish allergy include:
- Are my symptoms most likely due to an allergy?
- Will I need any allergy tests?
- Should I see an allergist?
- Do I need to carry epinephrine?
- Are there brochures or other educational materials I can have? What websites do you recommend?
Don't hesitate to ask other questions, as well.
What to expect from your doctor
Your doctor will likely have questions for you, such as:
- What symptoms are you having? How severe are they?
- When did you notice your symptoms?
- Have you reacted to shellfish in the past?
- What kind of shellfish did you eat?
- How soon after eating shellfish did your symptoms occur?
- What other foods did you eat during your meal? Don't forget sauces, beverages and side dishes.
- Did others who dined with you have similar symptoms?
- Is there a history of allergy in your family?
- Do you have other allergies, such as hay fever?
- Do you have asthma or eczema (atopic dermatitis)?
What you can do in the meantime
Avoid eating any type of shellfish before your appointment.