Hi there and thank you for the question. I am a Registered Nurse and will be happy to help you today.
This 'colored' liquid in these thermometers are usually consisting of ethanol and petroleum (and water and food coloring). To be on the safe side, I could contact Poison Control's hotline and let them guide you through the treatment process (if any)...they may just ask you to watch him or may have you take him to the ER for observation.
The phone number is XXXXX