There are different guidelines available, and they are different in the way they offer treatment..so which guideline do you follow with regard to allergic rhinitis ?
No matter what guidelines you chose to use, there is no guideline that could escape the following principles of the treatment of allergic rhinitis.
1). Work on prevention - Avoid exposure to allergen(s) as much as you can. Even, change a life style might help, like taking bath daily in the allergy season.
2). Medical treatment - you may start with a non-sedating anti-histamine. If it fails to work, follow it with the use of corticosteroid nose spray.
3). For a long term solution, if 1) and 2) failed to achieve a satisfactory result, you may consider an allergy desensitization, or immunotherapy treatment (it would be recommended for age 6 and above)
You could refer to your local guidelines and protocols, if they are not up to date, try the European Academy for Allergy and Clinical Immunology (EAACI) guidelines and position papers on allergic rhinitis / rhinoconjunctivitis. Even better, try the World Allergy Organization documents and guidelines, they are updated every year and are excellent.