What Is a Shellfish Allergy?

A shellfish allergy occurs when a person’s immunological system overreacts to the consumption of hard-shelled seafood. Though surprisingly common, shellfish allergies are unusual in that they often make their first appearance, without warning, in adulthood. Symptoms range from relatively mild to severe, sometimes life-threatening. Shellfish allergies are distinct from those for finned fishes. Experiencing one of these conditions does not necessarily mean experiencing the other.

If you undergo a severe allergic reaction to shellfish, seek medical attention immediately. The emergency department at any Baptist Health medical facility is ready to help you. If your reaction is relatively mild, contact your Baptist Health physician for consultation and treatment.

What Are the Symptoms of a Shellfish Allergy?

The symptoms of a shellfish allergy vary but include many of the following. Onset typically occurs shortly after consumption:

• Hives or rashes
• Labored breathing
• Stomach cramps and vomiting
• Strong cough
• Wheezing
• Throat constriction and difficulty swallowing
• Swollen tongue
• Weak pulse
• Pale or blue-tinged skin
• Dizziness and fainting
• Confusion

If symptoms are severe, or several occur simultaneously, you may be experiencing anaphylaxis, which is potentially fatal and considered a medical emergency. If you carry an epinephrine auto-injector, administer it immediately. Otherwise, go directly the nearest emergency-care facility.

What Causes a Shellfish Allergy?

Shellfish contains a protein called tropomyosin that can trigger a response from the human immune system. In more extreme cases, this response includes the production of histamines and an antibody known as immunoglobulin E or IgE. Overproduction of these chemical defenses can lead to symptoms such as hives, swollen respiratory passages, and difficulty breathing. Tropomyosin is typically ingested with food but can also be inhaled through the air anywhere seafood is being handled or prepared.

There are two main categories of shellfish, and being allergic to one doesn’t automatically mean that you’re allergic to the other. The first category, crustaceans, includes shrimps, crabs, and lobsters. The second category, mollusks, encompasses clams, mussels, scallops, oysters, and octopuses. Crustaceans are the primary source of shellfish allergies.

You are more likely to develop a shellfish allergy if other members of your family also have allergies. Adults are at a greater risk than children for shellfish allergies, with adult women more susceptible than adult men.

How Is a Shellfish Allergy Diagnosed?

Identifying any food allergy can be a complicated process. There is no single test for determining the existence of a food allergy as opposed to other medical conditions with similar symptoms. When attempting a diagnosis, your physician may pursue several avenues of inquiry, including:

• Documenting your symptoms: Which foods and in what quantities are causing you problems?
• Noting your family medical history: Do other members of your family have allergies (food or otherwise)?
• Conducting a physical exam: The exam’s purpose is the elimination of possible alternative causes to having a food allergy.
• Arranging a skin-prick test: Skin-prick tests look for evidence of reaction to a miniscule amount of the allergen.
• Arranging a blood test: Blood tests measure the level of immunoglobulin E, or IgE, an antibody manufactured by your immune system in response to the introduction of a food allergen.
• Designing an elimination diet: Certain foods are eliminated from, and then reintroduced to, your diet to ascertain their relationship to your symptoms.
• Conducting an oral-food challenge: An oral-food challenge is similar to the skin-prick test, except that food is introduced orally rather than topically.

How Is a Shellfish Allergy Treated?

There is only one sure way to forgo the problems associated with food allergies, and that is by avoiding your known allergens (and being cautious with other foods similar to them, for example, oysters if you’re allergic to lobsters). Avoidance is easier said than done. If you’re:

• Cooking your own meals, always check the ingredients listed on any package goods or processed foods you buy.
• Dining out, speak with your servers, chefs, or restaurant manager about the requirements related to your food allergies. Many restaurants publish their menus online so you can determine beforehand the safest items for consumption. You can also inform restaurants of your food allergies ahead of time when using internet booking applications.

Despite your best efforts, you may on occasion come into contact with a food allergen. Minor reactions can treated with over-the-counter or prescription antihistamines. More serious reactions call for the administration of epinephrine. Be sure to keep your epinephrine auto-injector with you at all times, and that you know how to use it. Make certain, too, that family members, or others who are close to you, know how to administer the drug as well.

When It Comes to a Shellfish Allergy, Baptist Health Can Help

If you suspect that you have a shellfish allergy, see your Baptist Health primary care physician or allergy specialist. He or she can determine the true nature and extent of your condition, and make recommendations for dealing with it. If you are in immediate need of help, please call 911 or seek emergency medical care.