Asthma and allergies can affect anyone, regardless of age, gender, race or socioeconomic factors. While it's true that asthma and allergies are more common in children, they can occur for the first time at any age. Sometimes allergy symptoms start in childhood, disappear for many years and then start up again during adult life.

Although the exact genetic factors are not yet understood, there is a hereditary tendency to asthma and allergies. In susceptible people, factors such as hormones, stress, smoke, perfume or other environmental irritants also may play a role.