Itchy nostrils are mainly due to irritation of the nasal mucosa. Histamine, bradykinin, protease and other substances irritate the nasal mucosa, resulting in mucosal oedema and increased mucus gland secretion, producing an itchy sensation.
Clear allergies can be treated with topical steroid hormone anti-allergy, but also with antihistamines such as cetirizine, loratadine and chlorpheniramine, and the anti-leukotriene drug montelukast.