Patch testing in lichenoid reactions of the mouth and oral lichen planus.

The role of allergic contact dermatitis in the pathogenesis of oral lichen planus⁄lichenoid reactions remains under controversy. The standard European, dental, organic mercurial and food batteries were applied to 53 patients with biopsy proven, symptomatic oral lichen planus between 1983 and 1988. There were 89 positive reactions in 39 patients. The patch test reactions were thought to be relevant in 21 patients only. Thus, it was concluded that the aetiology of oral lichen planus is still unknown but contact allergy may well play a significant role in its pathogenesis.