I was asked a question not so long ago concerning a dog and his sudden change of behaviour.
Here's the thing - the dog was ten years old. It lived in the same house for years without any problems. The owners of the house started digging new foundations for an extension and were changing the internal layout of the property causing disruption and dust and noise and all the other stuff that goes along with such work.
The dog was fine with the workmen, the mess etc. However since opening up the basement which had been sealed due to damp since before the owners moved in, he had been growling and barking at empty space, scratching at doors to get out of rooms, being destructive and biting the bottoms of the doors to escape. Howling at night and chasing around the house too. He was off his food and stared at his owners alot as well as past them. He was spooking them out but worse - the owners were considering having him put to sleep because his behaviour had changed so much that he was hard to live with. The vet had checked out the dog and could find nothing wrong and could only offer dementia and aging as a diagnosis.
The aging process is a possible solution but I would focus more on the change of energy that had invaded his environment.
The house is old and is on farmland that has been undisturbed for centuries. Perhaps there is an old burial site beneath it and the renovations had disturbed the ancestors buried there. It could be that a victim of crime is risen again after being freed from their hidden grave. It could be something that the builders had brought with them, a roaming or lost spirit. It could be the spirit of an animal. It could also be simply a change in the energy frequency caused by the land being disturbed. Or even an underground waterway that is affecting the energy of the house that sits above it because of the digging in the basement and surrounding area. Or electrical pylons, mobile phone mast, minerals in the water etc.
It could also be that the dog was reacting to his food or other foreign influence such as a poison or natural toxin he had access too.
It's important to consider all aspects when looking into such a case. Just because something appears to be paranormal doesn't mean it is and all logical explanations have to be looked at first.
Personally in this case I thought that there was a spirit of a boy in the house and that the building works had brought him to activity, but I could come to that conclusion because I had investigated properly using my senses and knowledge added to the fact that I could plainly see the spirit of the boy when I went to the house. That's where a trained medium becomes the only person able to deal with the energies being created and the spirit person that needs help. I spoke to the boy, assured him that nothing bad could happen to him anymore and that I could show him the way home to people who cared about him or to the angels who would look after him. After some convincing he allowed me to take him to the path that would lead him into the light and his recovery. He had been murdered by his father two hundred years ago and hidden in what used to be a pond. The boy guided me to the spot, which had been dug up by the builders and new concrete laid. He also guided me to a well in the grounds. No such well seemed to exist until the owner began to dig in the spot and found - you guessed it - an old well.
An exorcist would have banished the child, a witch removed him and cleansed the property but where would the boy go? A smudging or cleansing ceremony would not rid the building of its guest and a healer would not necessarily 'see' the spirit. Only a medium with clairvoyant or clairsentient or clairaudient abilities could help in this case, because the others had been tried by the owner of the house and had failed. As usual - I was a last resort before the men in white coats came to take people away. Sleep deprivation, arguments about differing opinions and lack of understanding meant that it took the owners three years before they found me and the 'problem' was cleared up in thirty minutes. There is a place for healers and mediums in our society, we do a valuable job that no-one else can do but the medium must be genuine, moralistic, compassionate and trained. I have done spirit rescue in lots of situations - some nicer than others - but it is always worthwhile and satisfying when done right, mistakes can be costly - to the medium.
The dog is healed, the house finished and everyone happy about a positive outcome.