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: Anaphylaxis was seen in 37 patients ( 69 % ) , the other 17 ( 31 % ) having urticaria and / or angioedema .
### Output Text:
Anaphylaxis was seen in 37 patients ( 69 % ) , the other 17 ( 31 % ) having urticaria and / or angioedema . 