Local nasal immunotherapy: experimental evidences and general considerations.

The possibility of local hyposensitization in allergies was envisaged since the first decades of the century and then sporadically employed, whereas controlled clinical trials of local nasal immunotherapy (LNIT) were performed only during the last 20 years. Studies currently available agree on the clinical efficacy of the treatment. LNIT was demonstrated capable of reducing symptoms both in pollen- and mite-induced rhinitis, and of modifying the specific target organ responsivity. Indeed, aqueous extracts appeared to be more effective than modified ones but were also charged by troublesome local side effects, while the recently introduced powdered extracts seemed to overcome this problem, maintaining a favourable clinical effectiveness. In a recent study we demonstrated a significant effect of LNIT on local allergic inflammation. LNIT reduced both the inflammatory infiltration and ICAM-1 expression on nasal epithelial cells upon specific nasal challenge. The effects on specific challenge appeared long-lasting, but the clinical efficacy seemed to depend strictly upon preseasonal treatment. LNIT with powdered extracts appears an effective, safe and well-tolerated treatment for allergic rhinitis. Nevertheless, its particular administration technique requires a careful choice of patients. Finally, a socioeconomical analysis shows a favourable cost/benefit ratio for LNIT if compared to classic subcutaneous immunotherapy.