Which is better for rhinitis and why? giving topical vasoconstrictor before topical steroid or vise versa?

Vaso before steroid: Some would say that steroid sprays may not be effective if the nasal tissue is swollen completely shut and the spray cannot get into the nose to do its job. In that case, opening the nasal passages with the decongestant first may help. If congestion is not that bad, it probably doesn't matter. Remember to use decongestant sprays for no more than 2-3 days at a time to prevent worsening of symptoms.

Both, timing is key: A topical vasoconstrictor helps as a decongestant very quickly but can cause rebound if used regularly. Topical steroids are the most effective treatment for allergies and do not cause rebound. If ones nose is extremely congested, use vasoconstrictor before nasal steroid, but limit vasoconstrictor to less than a week.