A number of medical specialties traditionally face changes and lesions in the mouth, specific for diseases seen routinely in their everyday practice: gastroenterologists, paediatricians, orthodontists, to name just a few, will easily identify the typical aspect of the tongue, the Koplik spots or a dysgnathia respectively, and the treatment of the underlying diseases in question will resolve the local problem. However, more unusual lesions with chronic or recurrent course may cause a much longer patient career, which may last for months or even years and is interspersed with more or less ineffective local antiseptic or steroid treatment regimens before underlying diseases like pemphigus, lichen, diseases of haematopoetic organs, paraneoplastic lesions or even simple mechanical consequences of parafunctions like bruxismus, are identified as the underlying cause. The otorhinolaryngologist, the dermatologist and the dentist-oral-maxillofacial surgeon offer an interdisciplinary consultation at the Center for Dental Medicine at the University of Basel, in which the advantages of an advanced diagnostic armamentarium and a combined pool of experience proves to be a gain for both the patients and involved medical persons. The otolaryngologist offers diagnostic procedures of the entire upper airways, the dermatologist bridges the gap to allergology, immunology and systemic diseases well known to his specialty. Dental medicine offers diagnostic and therapeutic alternatives, of which the first two have but scarce knowledge. In this article, the different approaches to the most frequently seen diseases and associated problems are described by the dermatologist and dental specialist. The dermatologist, in a succinct state of the art review, describes the problem of pemphigus and pemphigoid, diseases which may cause diagnostic problems because of their tendency to stay limited to the oral mucosa for a longer time. Recurrent aphtosis is another problem encountered frequently, in which a vast research effort has not yet abutted into pertinent knowledge on ethiology and effective therapy for all cases. The dentist-oral-maxillofacial surgeon is especially interested in the specific problem in the diagnosis and treatment of lichen planus i.e. the differentiation of true idiopathic lichen and the lichenoid reaction due to foreign bodies in the mouth. He describes the modern diagnostic and treatment procedures. In spite of missing parts in the puzzle of all these diseases, special consideration in every individual case contributes to more effective management and offers a gain in experience and knowledge to all medical persons involved.