What is the term for the exaggerated response of the immune system to certain antigens present in the environment?

Serotonin released from mast cells is responsible for.........

Assertion: Many visitors to the hills suffer from skin and respiratory allergy problems.
Reason: Conifer trees produce a large quantity of wind-borne pollen grains.

$A$ non-infectious,unnatural,and unusual reaction of a person to any substance or condition for which they are hypersensitive is termed as:

Many people suffer from which system-related problem due to pollen grains of many species?

Which chemicals are responsible for allergies?