Put by a layman, allergy would be nothing more than an unwelcome, often unpleasant reaction to certain external entity, stimuli or product. Almost all people have an allergy to something though the allergen has an inclination to differ from person to person. Listed below are some known causes that are generally answerable for allergy.

A number of folks have allergies to pollen. There have been many cases where people suffer hay fever or asthma due to the fact that they have allergies to pollen. Pollen is produced by just about each plant but the grass pollen is especially light. Wind carries this pollen far and wide. It gets stuck in the respiration system and to many causes breathing problems.