Guidelines from 2017 joint task force of Practice Parameters

“for initial treatment in adolescents and adults age over 12 monotherapy with an intranasal steroid is preferred: combining it with an oral antihistamine confers no additional benefit”

For moderate to severe allergic rhinitis, adding an intranasal antihistamine to an intranasal steroid can be beneficial.

An intranasal corticosteroid if used regularly is the most effective treatment for all allergic rhinitis symptoms