--- title: "Decongestants: Uses & Side Effects | HealthAnswers" description: "Decongestants relieve a blocked nose by shrinking swollen nasal blood vessels; sprays should only be used short-term to avoid rebound congestion." url: https://healthanswers.co.uk/treatments/decongestants/ robots: noindex --- # Decongestants: Uses & Side Effects | HealthAnswers Treatments Decongestants relieve a blocked nose by shrinking swollen nasal blood vessels; sprays should only be used short-term to avoid rebound congestion. Written by HealthAnswers editorial team Medically reviewed by [HealthAnswers UK doctor review panel](https://healthanswers.co.uk/our-doctors/) Reviewed 25 September 2026 ## Quick answer What are decongestants used for? Decongestants relieve a blocked nose by reducing swelling in the blood vessels of the nasal lining. They come as sprays, drops and tablets, and work well for short-term relief from colds, flu and sinusitis. Sprays should not be used for more than about a week, or congestion can rebound. General UK health information, not a diagnosis. In an emergency call 999 ; for urgent advice use [NHS 111](https://111.nhs.uk/) (GP out-of-hours in Northern Ireland). On this page 5 sections ## Key facts about decongestants - Decongestants reduce swelling in the nose to relieve blockage. - Decongestants are available as nasal sprays, drops and tablets from pharmacies. - They are for short-term use — sprays no more than about a week. - They do not suit everyone; check with a pharmacist. ## What are decongestants? Decongestants are medicines that relieve a blocked nose. They work by narrowing the swollen blood vessels in the nasal lining — it is that swelling, more than mucus, that creates the blocked feeling. They are useful short-term helpers for colds, [flu](https://healthanswers.co.uk/conditions/flu/) and sinusitis, available from pharmacies as sprays, drops and tablets. ## Using decongestants safely Sprays and drops act fast and directly; tablets work via the bloodstream and are often combined into cold-and-flu remedies. Two rules keep them effective and safe: - Keep it short. Nasal sprays should not be used beyond about 7 days — longer use causes rebound congestion, where the nose blocks up worse as each dose wears off. - Check the ingredients. Many combination cold remedies already contain a decongestant, so avoid doubling up. ## What are the side effects of decongestants? Decongestants do not usually cause side effects, and any that happen are usually mild. They can include: - feeling sleepy (non-drowsy versions are available) - irritation inside the nose - headaches - feeling or being sick - a [dry mouth](https://healthanswers.co.uk/symptoms/dry-mouth/) - feeling restless or agitated - a rash These usually go away once you stop the medicine. Very rarely, more serious effects such as hallucinations or a severe allergic reaction can happen. Call 999 if your lips, tongue or throat swell or you are struggling to breathe. ## Who should be careful with decongestants Decongestant tablets can raise blood pressure and heart rate, so check with a pharmacist first if you have [high blood pressure](https://healthanswers.co.uk/conditions/high-blood-pressure/), heart problems, glaucoma, diabetes, an overactive thyroid or prostate trouble, or if you take other medicines. Sprays act more locally but the same caution is sensible. ## Alternatives to decongestants with no time limit Saline sprays and rinses, steam inhalation, good hydration and sleeping slightly propped up all relieve congestion safely for as long as needed. For allergy-driven stuffiness, an antihistamine or [steroid nasal spray](https://healthanswers.co.uk/treatments/steroid-nasal-sprays/) usually suits better than a decongestant. See a GP if congestion persists beyond three weeks despite treatment. ## ! Important safety information for decongestants Check with a pharmacist before using decongestants if you have high blood pressure, heart problems, glaucoma, diabetes, an overactive thyroid or prostate problems, or take other medicines — decongestant tablets in particular can raise blood pressure. Do not use nasal sprays for more than about 7 days, as longer use causes rebound congestion. See a GP if congestion lasts more than 3 weeks. ## Common questions about decongestants How do decongestants work? They narrow the swollen blood vessels in the lining of the nose, reducing the swelling that causes the blocked feeling. Sprays and drops act directly and quickly; tablets work through the bloodstream. Why can't I use a decongestant spray for long? Using sprays beyond about a week causes "rebound congestion" — the nose becomes more blocked as the spray wears off, creating a cycle of dependence. Stick to short courses; saline sprays are a safe alternative for ongoing stuffiness. Who should avoid decongestants? People with high blood pressure, heart disease, glaucoma and certain other conditions should check with a pharmacist first, especially before tablet forms. Many cold remedies contain a decongestant, so check you are not doubling up. What else helps a blocked nose? Saline (salt water) sprays or rinses, steam inhalation, staying hydrated, and sleeping slightly propped up all help — and have no usage limit. For allergy-related congestion, antihistamines or steroid nasal sprays are usually more appropriate. ## Sources - [NHS — Decongestants](https://www.nhs.uk/medicines/decongestants/) ## How we reviewed this page Medically reviewed by the [HealthAnswers UK doctor review panel](https://healthanswers.co.uk/our-doctors/) First published 4 April 2026 Medically reviewed 25 September 2026 Next review due 25 September 2029 or sooner if NHS or NICE guidance changes Written by HealthAnswers editorial team. Published by HealthAnswers (Elite Digital AI Solutions Ltd). 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