Cairn terrier seperation anxiety

Question
My girlfriend's cairn is a little over a year old and has a terrible case of
seperation anxiety. When we leave to go somewhere he tries to force his
way out of the apartment with us if we don't crate him. He then scratches
at the door and barks, whines, and cries loudly enough to get neighbors
to complain. When we do crate him he cries incessantly. He has been
crate trained and he's fine in it so long as we're not leaving.

He's now taken to defecating and peeing when we're gone, both in and
out of his crate. In addition he will vomit when we get back. I've dealt with
dogs all my life and never encountered a problem this severe, much less
one that couldn't be solved with exercise and a full belly beforehand. He
had a recent trip to the vet to get checked out and he's medically sound.

It's putting a hurt on my relationship with my girlfriemd because she loves
him but hates to see his actions disturb me. We're researching
medications because training doesn't seem to stick with him and other
regular practices are ineffective. Before we take him back to the vet for a
consultation about meds, I was hoping to get some advice on any other
non-medicinal things we could try.

Answer
Well it seems like you have created a spoiled monster, huh? There are a lot of dog folk who believe there are no bad dogs - just the owners. I am not saying you are bad- you are just letting this pup rule the roost. You need to understand the nature of the beast. Medication most likely will not change the behavior if you both don't change with how you deal with this dog. It's all about the pack and your dynamic in the household. How you 2 treat each other and where he fits in. You need a behaviorist to come in and watch how everyone behaves and then you need to retrain yourselves. You didn't say how old the dog is but under NO circumstances stop using the crate. Once you do, he's won. Terriers are famously difficult if you don't have control in the first 3 years but they tend to calm down after
It's hard to help when I don't know your household so I would try to finder a trainer close by to work with.
Meanwhile - put the crate out of sight of the front door. Get a chew toy or fill a Kong hole with cheese and give it to him in there when you leave the house to take his mind off your leaving and DO NOT talk to him when you go. Ignore him.
And go find a good trainer- it pays off for all.
Cairns are a wonderful breed and really great housepets. Don't give up.
good luck!