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What are food allergies?

Get back to the basics with everything you need to know about the top 9 food allergies.  

What is a shellfish allergy?

Shellfish allergies are among the most common food allergies and can be quite severe. Shellfish encompass marine animals with shells such as shrimp, lobster and crab, as well as mollusks like scallops and squid. Some people are allergic to all shellfish, but others are only allergic to certain species. The two types of shellfish:

• Crustaceans with a hard exoskeleton, such as crabs, crayfish, lobster, shrimp, prawn
• Mollusks with soft bodies, such as clams, oysters, mussels, scallops, squid, snails, octopus

Allergies to crab, lobster and shrimp are the most common and reactions to crustaceans tend to be more severe, sending more people to the emergency room than any other allergen. Finned fish and shellfish are not related families of food, so being allergic to shellfish does not necessarily mean that one also needs to avoid fish. Contrary to popular belief, those with fish allergies do not need to avoid iodine and radiocontrast material in medical tests, as there is no relation between iodine and fish allergies.  

What is a sesame allergy?

Though sesame is not currently included on the list of Top 8 allergens, research indicates that sesame allergies are becoming increasingly common and can be life-threatening. Allergic reactions to sesame seeds and oil occur when the body's immune system mistakes the proteins in the seed as a dangerous invader and overreacts to attack it, prompting a reaction. Reactions range from gastrointestinal problems, hives and skin irritation to anaphylaxis. Sesame is the most common seed allergy, but other potential seed allergens include sunflower, poppy and mustard. Studies show that most individuals with a sesame allergy are not allergic to other seeds, meaning that doctors do not typically recommend automatic testing or elimination of other seeds. Researchers report that around 13% of individuals with peanut allergies also have an allergy to sesame, but around half of those with both peanut and tree nut allergies are allergic to sesame.  

What is a fish allergy?

An allergy to finned fish is among the top 8 most common food allergies and can be severe, potentially causing anaphylaxis, a life-threatening condition. As many as 40% of people reporting a fish allergy experienced their first allergic reaction to fish as adults, according to a study. Salmon, tuna and halibut are the most common fish to which people are allergic. Having an allergy to finned fish does not necessarily mean one is allergic to shellfish such as shrimp, crab or lobster, as there is no relationship between shellfish and fish. However, some people may have allergies to both shellfish and fish in the same way one would have an allergy to milk and peanuts. More than half of people who are allergic to one species of fish are allergic to all fish, so allergists tend to recommend that allergic people to avoid all fish. Some restaurants may also  swap out cheaper fish for another without notifying the customer, and there can be a high risk of cross-contamination when fish is prepared, especially in seafood restaurants. Speak with your allergist to undergo food allergy tests to discover which species of fish you can safely eat and whether or not you should avoid fish altogether. While having an allergy to fish protein (paravalbumin) is most common, some people may also be allergic to fish gelatin, made from fish skin and bones. People with a fish allergy should talk to their doctor before consuming fish oil supplements, which may contain molecules of the allergen Contrary to popular belief, those with fish allergies do not need to avoid iodine and radiocontrast material in medical tests, as there is no relation between iodine and fish allergies.  

What is a soy allergy?

A soy allergy occurs when the immune system mistakes the protein in soy as a threat to the body and reacts to attack it. This causes symptoms like rashes, stomach pain and trouble breathing. In rare cases, soy can cause anaphylaxis. This serious, potentially life-threatening reaction is more likely to occur in those who have asthma or other food allergies in addition to a soy allergy. Soy, also known as soya or soybeans, is a legume. Having a soy allergy is among the more difficult food allergies to manage because soy is in many processed and prepared foods. Soy is a common trigger of food protein-induced enterocolitis syndrome (FPIES) or a delayed food allergy that affects the gastrointestinal tract. Symptoms include vomiting, diarrhea and dehydration, which usually occur within hours of eating the allergen rather than minutes.  

What is an egg allergy?

Egg is one of the most common food allergies amongst children, second only to milk. Allergic reactions to egg occurs when the body's immune system mistakes the proteins in egg whites or yolks as harmful and overreacts against them. Symptoms of a reaction can range from as mild as an upset stomach up to as life-threatening as anaphylaxis. The proteins that cause an egg allergy are typically found in the egg whites rather than the yolks, but those with an egg allergy should avoid eggs altogether.