How do respiratory allergies affect the body?

Respiratory allergies occur when the immune system has a negative reaction to a particular airborne substance, like pollen, that's breathed in. Even though these substances are not really a danger to the body, antibodies in the immune system identify the allergen as a threat. This causes cells to release histamines, which cause inflammation in the area of the reaction. Most commonly, the areas affected by respiratory allergies include the skin, eyes, and airways.