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: Furthermore , it was found that the magnitude of attentional modulation in secondary hyperalgesia is very similar to that of capsaicin - untreated , control condition .
### Output Text:
Furthermore , it was found that the magnitude of attentional modulation in secondary hyperalgesia is very similar to that of <span class="chemical">capsaicin</span> - untreated , control condition . 