Global warming spurring more allergies?

Are global warming trends to blame for an increase in allergies among the world's population? How about the rise of asthma cases? It sounds pretty logical that the hotter the planet is, the more irritants can be found in the air we breathe, and hence we have more allergies and asthma cases.

The overall increasing amount of carbon dioxide in the air promotes the rapid growth of the plants whose pollen triggers quite a bit of this allergy madness (myself included).

What to do? Wear a face mask outside at all times? That would be off and probably not comfortable, but as greenhouse gases become more prevalent, some of us may need them.