Global Allergy Treatment Market Size, Trends, and Growth Opportunity, By Type (Eye Allergy, Food Allergy, Skin Allergy, Asthma, Rhinitis, Others), By Treatment (Anti-Allergy Drugs and Immunotherapy), By Route of Administration (Oral, Inhalation, Intranasal, Others), By End-Users (Hospitals, Specialty Clinics, Homecare, Others), By Distribution Channel (Hospital Pharmacy, Retail Pharmacy, Online Ph