N-acetylcysteine (NAC) is a preferred alternative to over-the-counter decongestants due to their vasoconstriction, rebound congestion, habit-forming potential, and lack of other health benefits.

“most decongestants are of the Alpha One Agonist variety what's an alpha 1 Agonist it causes Vaso constriction that Vaso constriction can be beneficial in preventing some of the intense congestion that one gets when you have a sinus infection or a cold or a flu but then when those decongestants wear off off one tends to get a rebound increase in congestion and it's really painful headache Etc in addition some over-the-counter decongestants can be habit forming not necessarily addictive but habit forming and they don't seem to have any other positive health benefits so I prefer not to take decongestant if I can avoid it