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: Baboon syndrome is a drug - or contact allergen - related maculopapular eruption that typically involves the flexural and gluteal areas .
### Output Text:
Baboon syndrome is a drug - or contact allergen - related maculopapular eruption that typically involves the flexural and gluteal areas . 