Which of the following is $NOT$ a symptom of an allergy?

Which one of the following diseases is due to an allergic reaction?

What are substances that trigger an allergy called?

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

Which of the following diseases is caused by an allergy?

Assertion : Mast cells in the human body release excessive amounts of inflammatory chemicals,which cause allergic reactions.
Reason : Allergens in the environment on reaching human body stimulate mast cells in certain individuals.