THE RATIONALE FOR USE OF TOPICAL CORTICOSTEROIDS IN ALLERGIC RHINITIS

The rationale for using topical corticosteroids in the treatment of al lergic rhinitis is that high drug concentrations can be achieved at re ceptor sites in the nasal mucosa, with minimal risk of systemic advers e effects. Topical corticosteroids have been demonstrated to reduce th e number of Langerhans' cells (or their markers) in the nasal mucosa, and this is thought to attenuate antigen presentation. T lymphocytes h ave been identified as being significant in orchestrating the immune-i nflammatory response, particularly the TH2 cells, which represent an i mportant target for topical corticosteroids. TH2 cell-evoked mast cell s and basophils are the sole producers of histamine, a mediator of maj or importance for rhinitis symptoms. Several studies have shown that t he increased number of mast cells and basophils in the epithelium foll owing antigen challenge/exposure, are markedly reduced by topical cort icosteroids. Furthermore, the number of eosinophils, an important morp hological marker of allergic rhinitis, can be profoundly reduced by tr eatment with topical corticosteroids. The rationale for topical treatm ent is strengthened by evidence of inhibition of cytokine release from surface epithelial cells, resulting in reduced recruitment and activa tion of mast cells, basophils, and eosinophils, which may be attribute d to the high drug concentration achieved in epithelial cells. Ongoing inflammation in the mucous membrane is indicated by entry of plasma i nto the nasal lumen which subsides with the anti-inflammatory efficacy of topical corticosteroids. In contrast to antihistamine therapy, whi ch has little effect on nasal blockage, pretreatment with topical cort icosteroids results in almost complete attenuation of late-phase sympt oms including nasal blockage, and moderate efficacy in early phase sym ptoms. Clearly, the spectrum of anti-inflammatory activity afforded by topical corticosteroid therapy is of clinical significance in reducin g the three major symptoms of allergic rhinitis - sneezing, watery rhi norrhoea and nasal blockage.