Yes, you can eat seaweed if you have a seafood allergy, but you should eat it with caution. Seaweed does not contain any fish proteins or any other seafood properties. However, if you have a seafood allergy, MayoClinic.com warns that you should avoid eating at any seafood restaurants -- even if you don't order a dish containing fish. A plant found in salt water, seaweed is commonly used in Asian cuisine, including sushi.
You can technically eat seaweed if you have a seafood allergy, because seaweed does not contain any fish protein. Protein found in the flesh of fish is what causes an allergic reaction, according to the Asthma and Allergy Foundation of America. When you consume seafood, the immune system doesn't identify the proteins in the fish as safe, so it reacts by attacking the proteins. This causes an allergic reaction. If you're allergic to one type of fish, you may or may not be allergic to other types of seafood. Your doctor can perform allergy tests to determine which seafood you can eat safely.
Cross-contamination needs to be considered before you eat seaweed. Although seaweed doesn't contain any fish proteins, if prepared in a kitchen or facility that also prepares seafood, seaweed may become contaminated with fish proteins through shared countertops, utensils and cookware. For example, if you eat at a sushi restaurant and order a roll that's vegetarian, the same countertop that's used to make fish-based sushi is used to make your veggie roll. The proteins on the countertop can transfer onto the seaweed, causing an allergic reaction.
If you experience any allergy symptoms after eating seaweed, call your doctor. Seafood allergies are a common cause of anaphylactic shock, according to MayoClinic.com. Anaphylactic shock is a severe allergic reaction that causes your entire body to experience a reaction. This can cause your lungs, airways and throat to swell, which can cut off your ability to breathe, leading to death.
Less severe symptoms of a seafood allergy include asthma, skin rashes, digestive complications, nasal congestion and facial swelling. Any symptoms need to be evaluated by a medical doctor immediately. It is best if your doctor can assess your symptoms as they are occurring.