Context : The observed spectral variation of HD 50138 has led different authors to classify it in a very wide range of spectral types and luminosity classes ( from B5 to A0 and III to Ia ) and at different evolutionary stages as either HAeBe star or classical Be .

Aims : Based on new high-resolution optical spectroscopic data from 1999 and 2007 associated to a photometric analysis , the aim of this work is to provide a deep spectroscopic description and a new set of parameters for this unclassified southern B [ e ] star and its interstellar extinction .

Methods : From our high-resolution optical spectroscopic data separated by 8 years , we perform a detailed spectral description , presenting the variations seen and discussing their possible origin .
We derive the interstellar extinction to HD 50138 by taking the influences of the circumstellar matter in the form of dust and an ionized disk into account .
Based on photometric data from the literature and the new Hipparcos distance , we obtain a revised set of parameters for HD 50138 .

Results : Because of the spectral changes , we tentatively suggest that a new shell phase could have taken place prior to our observations in 2007 .
We find a color excess value of E ( B-V ) = 0.08 mag , and from the photometric analysis , we suggest that HD 50138 is a B6-7 III-V star .
A discussion of the different evolutionary scenarios is also provided .

Conclusions :