Asthma, atopic eczema (dermatitis), drug allergy, food allergy and food intolerance, rhinitis, and skin allergy are the most common conditions that allergists treat. The majority of allergic disease occurs in childhood. Often, two conditions coexist. Allergies, including asthma, are among the most common chronic conditions worldwide. The most common allergic triggers are pollen, dust, grass, food, insect stings, animal dander, mold, medications, and latex.