By the time I get to see a dog whose behavior is so nervous their quality of life is compromised the dog is reacting to just about anything. It often starts with one issue and then spreads over time. There is one common factor, their owners have rewarded and encouraged the behavior however unwittingly and the real level is usually lower than it appears.
The basic rule is to always use voice encouragement but never touch until the moment has passed. Use a confident “I'm not bothered by the problem, I'm not scared” voice not a baby voice and confident body language. Try to stand upright, make big hand gestures, look confidently at the dog. Don't stand there thinking “Oh my God, my poor dog”, it doesn't help, you just communicate your own panic and add to the problem.
Dogs can be great actors. They sometimes learn that cowering, shaking and skulking away is a great way of not doing what you asked. Always follow through commands, calmly and gently.
Leaving The HouseTrue separation anxiety (SA) is rare. A dog with SA is a very timid, insecure dog who cannot cope even when you are there. It seems that any dog who barks, chews, messes or hurts themselves when left is automatically diagnosed with SA. True SA is a dog who is clingy, nervous and shows some of the same symptoms even when you are with them. Most of the dogs who have SA are dogs with dominance issues or who are bored, lack enough exercise and stimulation or no manners or training.
If your dog is happy normally, but barks the place down or wrecks it when left alone, think about proper training, games, toys and better exercise. If your dog lacks respect, jumps all over everybody, doesn't obey commands properly and steals your food, it doesn't have SA, it needs training.
When you leave, leave calmly, put the dog in its normal place, say “see you later”, leave it something to do and just go. Don't stand there saying “Please be good, don't chew anything, please be quiet” or you can guarantee they will do exactly that because you make them anxious then leave.
TriggersIf your dog starts to react as soon as you do something that makes it guess you are leaving, desensitizing with no result is the best treatment. So if, for example, picking up your keys sends the dog into a frenzy, leave the keys somewhere obvious. Every time you pass them, pick them up and put them straight down. Ignore the dog and carry on about your business. When you get to the point you can pick them up and get no reaction, praise the dog. Use the same trick with lifting your coat or shoes until the dog hardly bothers.
Start small and stay calm. You are trying to break the association of the first behavior and the assumption that you are going out.
ConfidenceIf your dog is a very clingy, insecure dog it will never get better if you consistently pander to it. If your dog jumps at loud noises, don't run to it and start picking it up, petting it and sounding anxious yourself. Look at the dog, wave your hand and say “not a problem, look, I'm not bothered” and carry on. Don't ignore it, just look and sound like you don't care. If the dog is afraid of an item, go to it, pick it up, calm, confident voice, say “look, this is fine, not scared” and walk away. Don't take the item to the dog and don't try to force the dog towards it.
Dogs pick up on your signals and high pitched, baby talk sounds like panic. Constant stroking rewards and stimulates the adrenalin so you are not making it better.
TreatmentYour own behavior is the most successful way forward. Calm assertive body language, saving the real attention for the calm dog moments. Bach Flower Remedies can help a lot in genuine cases of SA and of fear related behavior but it must be diagnosed properly and the right ones used, do not use Rescue Remedy as a cure all. Don't let your dog live like this, get some professional help.