Shellfish Allergy: What Symptoms to Look Out For And How It is Diagnosed and Treated
Shellfish is the leading cause of self-reported food allergy in the U.S. It affects about 3% of adults and just over 1% of children.
People with a shellfish allergy may react to one or more foods in the same shellfish family. This is different than having an allergy to finfish.
Some types of shellfish resemble each other in body shape. For example, if you are allergic to one crustacean (such as shrimp, crab, or lobster), you are more likely to be allergic to another. Something similar is also seen with mollusks (such as clams, oysters, and mussels).
What causes shellfish allergies?
Food allergies are caused by an overreaction of the immune system. A food allergy occurs when the body mistakenly identifies a food substance (known as an allergen) as a foreign invader. This causes an army of immune agents to work to eliminate the invader (known as a reaction). These reactions manifest as an allergy.
There are many allergens that can cause a shellfish allergy. The crustacean group, which includes shrimp, lobsters, and crabs, causes the most reactions.
What are the symptoms of shellfish allergy?
Shellfish allergy can cause a strong immune response. Within 60 minutes of eating the allergen, people who are allergic to shellfish may experience:
- itching in the mouth and throat
- swelling of the lips
- skin reactions, such as hives, swollen eyes, and red skin
- In some people, an allergic reaction to shellfish can be severe and potentially life-threatening. This is called anaphylaxis. Symptoms may include:
- coughing, wheezing, or difficulty breathing due to constriction of the airways
- severe abdominal pain
- vomiting
- diarrhea
- low blood pressure
- dizziness or fainting
- In rare cases, allergy can lead to death without immediate treatment with epinephrine. Epinephrine comes in many forms that can be injected or sprayed into the nose. EpiPen is just one of several options for allergy treatment. Each works differently, so be sure to check with your pharmacist.
What are the standard diagnostic tests for shellfish allergy?
The doctor begins by reviewing the person’s allergy history and referring them to an allergist. At the allergist’s office, specialists review the patient’s entire history.
The patient might undergo skin tests or blood tests to help confirm a shellfish allergy. However, these tests are not accurate in all situations. They cannot be used to predict a reaction. They can only confirm afterward that a reaction was related to a food.
Doctors would then decide if an oral food challenge is necessary to confirm a diagnosis. A food challenge is an office visit where the patient would eat the food in question in small amounts while being observed. Health care professionals will monitor for any signs of reactivity and treat accordingly.
How long does it take for shellfish allergy to go away, if at all? Does shellfish allergy go away over time?
Most people do not outgrow their shellfish allergy. In general, a small percentage of patients report that they have outgrown their allergy.
People who want to know if their allergy has resolved should see an allergist for further evaluation. In the meantime, they should avoid the food that may be causing their allergy. They should also keep epinephrine on hand in case of accidental ingestion.
What role does immunotherapy play in the treatment of allergies?
Oral and injectable immunotherapies can reduce patients’ sensitivity to specific foods. They may lessen a reaction in the event of accidental exposure to a food, but they do not cure a food allergy.
Patients receiving food-directed immunotherapy should avoid the offending food outside of their treatment. They should also carry injectable or nasal epinephrine with them in case of accidental ingestion.
What are some possible treatments for an allergic reaction?
In the case of accidental ingestion, treatment for an allergic reaction is based on symptoms. Treatments include antihistamines, injectable epinephrine, and breathing treatments, if necessary.
If you suspect you are having an allergic reaction to a food, you should be evaluated by a medical professional. He or she can determine possible treatment and monitor symptoms going forward.
Corticosteroids (such as prednisone or prednisolone) have not been shown to affect the treatment or outcome of an allergic reaction. Your doctor can tell you if these may be helpful.
Secondary therapies, such as oral immunotherapy or biologic immunotherapies, help suppress the severity of reactions. These are not used to treat immediate reactions or to cure food allergies.
