Your risk of developing allergies depends largely on whether your parents were allergic to anything. If both of your parents have or had food allergies, you have about a 75 percent chance of also being allergic to some type of food. If just one of your parents is allergic, your chance sits somewhere around 30 or 40 percent. But if neither of your parents has an allergy to food, you only have about a 10 or 15 percent chance of getting a food allergy. When it comes to shellfish allergies, you're most likely to develop them after you've passed childhood. Many times, shellfish allergies only appear once you become an adult, and then they rarely go away.
The allergy itself is your body's overreaction to certain proteins found in shellfish. When you eat specific types of shellfish, your body identifies those proteins as dangerous invaders and releases antibodies to attack them. Then those antibodies send out other chemicals to combat the allergens, and you suffer allergic symptoms as a result. Common symptoms of a shellfish allergy include hives, rashes, swelling, congestion, difficulty breathing, diarrhea, nausea, vomiting, dizziness, a tingling in the mouth and even anaphylaxis on rare occasions. Any of these symptoms can set in within minutes to hours of eating shellfish.
Just because you're allergic to one type of shellfish doesn't necessarily mean you're allergic to other types. For instance, an allergy to calamari doesn't have to mean you can't eat shrimp. However, it often does. After a doctor has diagnosed your shellfish allergy, your best bet is to stay away from all kinds of shellfish. Since it's a common allergen, products that contain any type of shellfish are labeled as such. When avoiding shellfish, it's also important to clarify what you're getting at restaurants when you order. You don't always know what ingredients are in your food, and sometimes shellfish are fried in the same oil as other restaurant offerings.