Credit: Getty Images

Shellfish is another allergy that can develop in adulthood and is unlikely to go away. Approximately 60 percent of people with shellfish allergy don't experience their first allergic reaction until adulthood. People who are allergic to shellfish are likely to react to both crustacea (like lobsters, crabs, shrimp) and mollusks (like clams, mussels, oysters, and scallops). Beyond avoiding foods and products with shellfish, people with this allergy should be careful to keep out of steam produced by shellfish cooking, which can also cause an allergic response.