In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Continuous topical use of immunomodulators such as tacrolimus or pimecrolimus should be regarded as a potential cause of rosaceiform dermatitis , although many cases have not been reported .
### Output Text:
Continuous topical use of immunomodulators such as <span class="chemical">tacrolimus</span> or <span class="chemical">pimecrolimus</span> should be regarded as a potential cause of rosaceiform dermatitis , although many cases have not been reported . 