Are Shellfish And Fish Allergies The Same Thing?

Shellfish and fish are among the top eight major food allergens identified by the U.S., according to the U.S. Food & Drug Administration (FDA) — in case you're curious, the other six are wheat, soybeans, milk, eggs, tree nuts, and peanuts. While the FDA lists shellfish and fish as two separate allergies, it may leave you wondering why, since both are seafood and share the mutual word "fish." But is there a difference?

Biologically speaking, shellfish and fish are indeed completely different (via Nemours KidsHealth). Fish are animals that are aquatic vertebrates (i.e. salmon or tuna), while shellfish are aquatic invertebrates (i.e. crabs or clams), according to an article in The Journal of Allergy and Clinical Immunology: In Practice. Shellfish can also be broken down further into two distinct categories: mollusks (i.e. clams, oysters, and squid) or crustaceans (i.e. shrimp, lobster, and crabs).

When it comes to seafood allergies — allergies to fish or shellfish – Healthy Eating Advisory Service points out that people typically have a food allergy to one or the other, but not both. Those with shellfish allergies can be allergic to both categories of shellfish, but again, not all people are (per Nemours KidsHealth).

What happens when you have a seafood allergy?

Seafood allergies are more common in adults than young children, and approximately one out of 100 people have allergies to seafood (via Better Health Channel). When a person is allergic to either fish or shellfish (or any other food), the body's immune system overreacts to certain proteins found within the seafood (per Nemours KidsHealth). It then releases chemicals called histamines since it believes the allergens are toxic invaders. When this happens, an allergic reaction occurs.

These reactions may vary in severity and from person to person. Some common symptoms shared by Nemours KidsHealth include wheezing, stomach pain, diarrhea, vomiting, hives, and swelling. In some cases, shellfish or fish allergies can be life threatening. This is called anaphylaxis, or a severe allergic reaction. According to Better Health Channel, symptoms of anaphylaxis include difficulty breathing, throat tightness, tongue swelling, and collapsing.

For this reason, if you have a fish allergy, it's best to avoid all fish and products that may contain fish ingredients, such as tuna, mackerel, cod, trout, anchovies, sushi, some salad dressings, fish sauce, and products fortified with omega-3s (per Healthy Eating Advisory Service). If you're allergic to shellfish, Healthy Eating Advisory Service recommends forgoing prawns, lobster, mussels, octopus, abalone, scallops, squid ink, prawn crackers, and Asian food, among other potential culprits. Finally, if you suspect you have a serious food allergy to either fish or shellfish, chat with your doctor immediately, as you may need an epinephrine auto-injector for emergencies.