Can montelukast become an alternative of allergens immunotherapy for perenial allergic rhinitis?

Not really. I suggest 3 steps to controlling allergies : 1) avoid the things you are allergic to. 2) take medications to control the symptoms. 3) get 'allergy shots' (immunotherapy) to teach your body to not be "allergic" to those things (immune tolerance). Using a leukotriene antagonist control the symptoms some, but it is not the most effective medication, and is not an equal alternative to immunotherapy.