Xylometazoline, also spelled xylomethazoline, is a medication which is used to improve symptoms of nasal congestion, allergic rhinitis, and sinusitis. Xylometazoline was patented in 1956 and came into medical use in 1959. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. The drug works by stimulating adrenergic receptors on the lamina propria of blood vessels in the nose. The decongestant effect is due to constriction of large veins in the nose which swell up during the inflammation of any infection or allergy of the nose. The smaller arteries are also constricted and this causes the colour of the nasal epithelium to be visibly paler after dosage. The standard adult solution strength is 0.1% w/v xylometazoline (or 1 mg per 1 mL solution), and the dose for children under 12 is usually 0.05% (0.5 mg/mL).