Mr Meacher argued that some GM substances had already been found to cause allergic reactions, he said.

BBC: GM crops

About 60% of the 17 million U.S. asthma sufferers are allergic asthmatics, meaning that their asthma attacks can be triggered by allergic reactions to pollen, dust or other normally harmless substances.

FORBES: Magazine Article

An allergist tests to see which plants you are allergic to, and then gives injections of tiny doses of those offending substances so that you become desensitized.

CNN: Global warming brings on more pollen