Exposure to animals early in life might reduce the risk of developing these specific allergies. Several different types of medications reduce allergic symptoms: including nasal steroids, antihistamines, such as diphenhydramine, cromolyn sodium, and leukotriene receptor antagonists such as montelukast. Oftentimes, medications do not completely control symptoms, and they may also have side effects. Exposing people to larger and larger amounts of allergen, known as allergen immunotherapy (AIT), is often effective. The allergen can be given as an injection under the skin or as a tablet under the tongue. Treatment typically lasts three to five years, after which benefits may be prolonged.