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 , we evaluated whether some factors have the potential to increase the risk of reaction to paracetamol and nimesulide .
### Output Text:
Furthermore , we evaluated whether some factors have the potential to increase the risk of reaction to <span class="chemical">paracetamol</span> and <span class="chemical">nimesulide</span> . 