Introduction 
Pemphigus vulgaris and lichen planus are one of the important skin diseases which involve oral mucosae,
The patients often suffer from extensive and diffuse ulcers in their oral cavity which are refractory to the routine treatment. Mainstay of treatment in these patients is systemic use of corticosteroids which can be associated with side effects such as Hypertension , Hyperglycemia, Osteoporosis , etc.
The aim of this study was to evaluate the effects of topical corticosteroid therapy added to systemic therapy to accelerate healing of oral lesions and decreasing systemic use of corticosteroids .
Materials & Methods
In this study after synthesis of dexamethason 0.1% mouth wash ( DM ) ( in Pharmacology School of Mashhad University of Medical Sciences, ), its therapeutic effects on  20 patients with oral lesions of pemphigus vulgaris and erosive lichen planus were evaluated and compared with routine treatment methods .
Results
Statistical analysis revealed that DM could decrease the pain of oral lesions in pemphigus significantly (P=0.02) and fulfilled patient’s demands, but this effect was not significant for lichen planus lesions . DM could not reduce ulcers duration in any of the diseases.
Conclusion
 Since reduction of pain as well as  burning of oral lesions could indicate inflammation decrease and initiation of healing, doing additional studies with higher concentration of this mouthwash or longer time use is recommended.