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: Nineteen patients ( 48 . 7 % ) substantially improved after the 8 - week trial ; 5 ( 12 . 8 % ) discontinued therapy due to side - effects such as intolerable capsaicin - induced burning sensations ( 4 ) or mastitis ( 1 ) ; 15 ( 38 . 5 % ) reported no benefit .
### Output Text:
Nineteen patients ( 48 . 7 % ) substantially improved after the 8 - week trial ; 5 ( 12 . 8 % ) discontinued therapy due to side - effects such as intolerable <span class="chemical">capsaicin</span> - induced burning sensations ( 4 ) or mastitis ( 1 ) ; 15 ( 38 . 5 % ) reported no benefit . 