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: These cases confirm the necessity of avoiding alcohol consumption as recommended in the instructions for use of Dormex and of preventing cutaneous contact during use .
### Output Text:
These cases confirm the necessity of avoiding <span class="chemical">alcohol</span> consumption as recommended in the instructions for use of <span class="chemical">Dormex</span> and of preventing cutaneous contact during use . 