The pathophysiology of RM is unclear, although several mechanisms involving norepinephrine signaling have been proposed. RM is associated with histological changes that include: an increase in the number of lymphocytes and fibroblasts, epithelial cell denudation, epithelial edema, goblet cell hyperplasia, increased expression of the epidermal growth factor receptor, increased mucus production, nasociliary loss, inflammatory cell infiltration, and squamous cell metaplasia. Direct acting sympathomimetic amines, such as phenylephrine stimulate alpha adrenergic receptors, while mixed-acting agents, such as pseudoephedrine can stimulate both alpha and beta adrenergic receptors directly and indirectly by releasing norepinephrine from sympathetic nerve terminals. At first, the vasoconstrictive effect of alpha-receptors dominates, but with continued use of an alpha agonist, this effect fades first, allowing the vasodilation due to beta-receptor stimulation to emerge. 2-Imidazoline derivatives, such as oxymetazoline, may participate in negative feedback on endogenous norepinephrine production. Therefore, after cessation of prolonged use, there will be inadequate sympathetic vasoconstriction in the nasal mucosa, and domination of parasympathetic activity can result in increased secretions and nasal edema. Evidence suggests that if oxymetazoline is used only nightly for allergic rhinitis (instead of more frequent dosage as may be directed on product label), it may be used longer than one week without high risk of<unk>  especially with use of intranasal steroid like fluticasone furoate.
Rhinitis medicamentosa
Contact stomatitis
Lymphedema–distichiasis syndrome
Fusariosis
Acheiria
Streptococcal intertrigo
Visceral larva migrans
Honeymoon rhinitis