Allergies
The immune system consists of a complex set of factors used to distinguish self from foreign; This system protects against external pathogens and avoid an adverse response against components of the organism itself; but about 17% of the population has some type of hypersensitive immune response against any particle, which we call allergen that produces a harmful effect on the host itself, this response being known as allergic reaction. This can be inhaled allergen (dust, mold, pollen, etc.); ingested (certain foods), insect stings, drugs or by contact. The hypersensitivity reaction initiated releases substances that cause allergic symptoms: nasal obstruction, sneezing, runny nose, itching, headache, sore throat, cough and dark circles.