Hello XXXXX,
Thank you for using Justanswer for you question.
This is refered to as "Separation anxiety" (besides separation anxiety, the toddler usually has stranger anxiety around this same time - usually occurring from 9 to 12 months and can last unto 18 to 24 months of age.) The vomiting seems a little extreme, but it may be very well within the normal limit. This shows how well your baby is attached to you, which is a good thing. Try to spend time with him before you leave and comfort and explain as much as possible that you will be back. You should start to see some change in the next few months. Sometimes children will get a "transition object" at this age, like the cartoon character Linus has a blanket, a child will will often use a stuffed animal or blanket that they keep with them as a comfort object that helps them get through the time when you are away. The brain and cognition will continue to grow and he will eventually understand that you are "there" even when he can not see you. When you leave, and he has this strong reaction it is because he feels like he will never see you again. Until the time he understands better you may want to give him a favorite stuffed animal or object and see if that helps.
This is explained here as well: http://wondertime.go.com/learning/child-development/development-social.html
Here is more information too on ways to handle this: http://www.babycenter.com/0_separation-anxiety_145.bc
Let us know how this works out for you.
Take care, Susan
Nurse (RN)
BSN, MSN, CNS