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: The notable fact was that this complication occurred in three patients hospitalized before treatment began , with whom particularly strict therapeutic precautions were taken , i . e . , initial dose less than 10 mg of DEC , very gradual dose increases , and associated anti - allergic treatment .
### Output Text:
The notable fact was that this complication occurred in three patients hospitalized before treatment began , with whom particularly strict therapeutic precautions were taken , i . e . , initial dose less than 10 mg of <span class="chemical">DEC</span> , very gradual dose increases , and associated anti - allergic treatment . 