Genetic tendencies play a role since allergies tend to run in families. You might not be allergic to the exact same things as them, but if one or both of your parents have had seasonal or year-round allergies, you're likely to as well.

That said, allergies can develop at any age, though a person will usually develop allergies during childhood or early adulthood.

Environmental exposure may also play a role in triggering allergies. For example, some people who are consistently exposed to allergens (e.g., people whose work exposes them to seed dust) may be more at risk of developing allergies. Research has also shown that infants exposed to cigarette smoke may be at increased risk for allergies.