Kevin White5 said:First off—the woman at the pharmacy is a pharmacist, and she isn't qualified to give medical advice regarding side effects or how to manage specific conditions like allergies or viral infections. That is strictly a doctor's job.
A pharmacist is an expert—they know their drugs, indications, and side effects. In fact, they play a vital role by advising patients on what they are buying (which is why pharmacists sell medication, not bakers) and even reminding us doctors about usage protocols when needed.
And rightfully so, she advised the patient not to use decongestants for more than a week during a cold.
If the nasal inflammation is "vasomotor" in nature, a physician might prescribe long-term vasoconstrictors.
Otherwise, for standard colds, vasoconstrictors are prescribed only briefly—just enough to reduce swelling, allow sinus drainage, and prevent sinus infections or bacterial superinfections.
With vasoconstrictors, the blood vessels eventually "adjust" to a daily dose; once that dose stops—even after the cold is gone—the mucosa produces excess fluid (exudate), leading to a stuffed nose the moment you stop using the drops. A congested nose (swollen mucosa) is, unfortunately, a perfect breeding ground for bacterial infection.
Most viral infections clear up within those seven days of using nasal drops or sprays. If the cold persists, several things could be happening.
1) It might not have been a viral infection at all, but rather an allergy—meaning the nasal mucosa stays inflamed as long as the allergen is present, unless one starts using allergy medication (like antihistamines).
2) A bacterial infection may have already developed, requiring antibiotics.
3) It could be a vasomotor reaction where the mucosa inflames due to temperature changes, alcohol, spices, or emotional stress... one must evaluate if treatment is even necessary and, if so, which class of medication to use.
If the nasal mucosa has already become "accustomed" to drops and sprays, a good way to transition away is using saline solutions—sprays that moisturize the passages and soften mucus to make blowing your nose easier without creating or maintaining a "dependency."
By the way, decongestants can trigger heart arrhythmias, particularly in predisposed individuals. More common side effects include jitteriness, tremors, and peripheral vasoconstriction—which should be avoided in cases of Raynaud's phenomenon...