What causes allergies?

Hypersensitivity to foreign substances, which are normally harmless, is called as allergies.  However, this hypersensitivity may lead to violent reactions in the human body.  In simple words, allergy means elimination of unsuitable substances by the body system.

Though there are many forms of allergies Chronic Allergies and Nasal Allergies are the most common forms.  Term Nasal Allergy refers to the occurrence of allergy within the cells of nose lining.

The other form, Chronic Allergies, is comparatively serious in nature than that of Nasal Allergies.  A person suffering from chronic allergies may develop nasal allergies and can also be get affected by non-allergic stimuli.  Cold air, dry air, particles present in the air and smoke are some of the examples of non-allergic stimuli.  The prevention methods for both, chronic allergies and nasal allergies are identical.  While adopting the preventing measures it is important to know other forms of allergies or other substances that can lead to allergies.  Dust mites, animal dander, mold spores, dust and pollens are some of the common allergens. 

Though the allergies are usually harmless in severe cases they could lead to minimal brain dysfunction and faulty thinking, especially in children.  A sizeable population in the United States suffers from various allergies.