GILLAN SHEPHERD, MD: When grass pollen enters, it'll bind with this allergy protein, which releases a lot of chemicals and most people are familiar with the one, histamine. It also induces a lot of itching, eyes, nose, sneezing.
ANNOUNCER: A common misperception about allergies is that they only become active at certain times of the year.
GILLIAN SHEPHERD, MD: A lot of people think allergies only happen in the spring or fall, but actually there are two types of allergy problems. One is what we call seasonal, and certainly it happens typically in the spring. And that is due to tree pollen. Then in the summer it's due to grass pollen. And in the fall it's due to the pollens of weeds, notoriously ragweed .
However in addition to being seasonal a lot of allergies are what we call perennial. They're there throughout the entire year. And these are the people that are allergic, for example to dust mites in their home, to the pets in their home. In some areas of inner city, cockroach allergy is a major problem. And in a lot of parts of the country, mold allergy is a major problem.
ANNOUNCER: For many allergy sufferers, everyday life can be negatively affected by their symptoms.
ELI MELTZER, MD: I have people who come to see me because they're socially impaired because they can't visit certain houses because there's an animal.
EVE RUBENSTEIN, MD: I can't go to people's houses who have cats because that's still a real problem for me.
