There are 2 levels here; getting it right within the company, and secondly the presentation of you/company to people outside. In many cases for IT professionals they are the hidden and critical component in the background of the company so don't represent the company in any public way. Therefore the correct dress code represents mainly what is socially acceptible within the office and your co-workers and boss considers acceptible - not just dress code either. If your role is to represent the company outside then clearly you should represent that company as part of your job. You don't look/smell a mess in front of people outside just like you would not a write a defamatory email.