My DTs (2.6) have developed a fear of most animals, but particularly dogs. We have a dog (albeit a very small yorkshire terrier ) who we had before they were born so they have grown up with dogs. My mother has a dog, as does my SIL and various other friends and family and up until a few months ago they were quite happy to be around them - to the point of climbing all over my mum's (quite large, but v. gentle) dog when they were younger. I really can't pinpoint exactly what happened to prompt this fear but it is quite extreme - they now become hysterical if another dog comes close to us in the park and my SIL had to keep her two dogs shut away the last time we spent the day there. When our dog was last groomed they were terrified of him for a while as well because they didn't recognise him. It's not just big dogs...they're terrified of small ones too!
I'd really like to try and help them over this, but don't know how, so any suggestions would be gratefully received. My mum's invited us for Xmas, and it would be difficult to go and have to ask her to keep her dog on a lead the whole time!