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: Drowsiness and altered taste perception were increased significantly over placebo only in the high - dose azelastine group .
### Output Text:
Drowsiness and altered taste perception were increased significantly over placebo only in the high - dose <span class="chemical">azelastine</span> group . 