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: All patients had gustatory hyperhidrosis , which interfered with their social activities , after transthroacic endoscopic sympathectomy , and which was associated with compensatory focal hyperhidrosis .
### Output Text:
All patients had gustatory hyperhidrosis , which interfered with their social activities , after transthroacic endoscopic sympathectomy , and which was associated with compensatory focal hyperhidrosis . 