itching and constant grooming

Question
I have a 17 month old cocker spaniel and a 10 year old cat.They are constantly digging and scratching and the cat grooms continually and throws up furballs as a result. They have been to the vet. and there are no fleas, no floating dandruff, no broken skin from the digging and scratching. I've changed the dogs diet but not the cats as he's been on the same food long before the grooming and scratching began. I thought it might be from the heat of the woodstove but that's not being used now, and the problem persists I've steam cleaned the carpets but they both dig and scratch outside as well. Their coats are shiny and they eat well and drink water and are healthy.I've given them omega oil and very rarely bath them so it won't dry out their skin. I'd never try to bath the cat anyway.I have a spray the vet gave me for hot spots called Dermacool but it doesn't help. I am at my wits end and they must be so uncomfortable constantly scratching and grooming. The cat never did that and we've had him for over 3 years and neither did the dog until a few months ago .Nothing has changed here, no new furniture, no scented candles or sprays. I hope you can help. My house is full of clumps of hair which I am vacuuming daily. I wonder why their skin isn't broken with the constant chewing and biting. The dogs teeth will chatter as I brush him and he nibbles on my arm as if he's so, so itchy.It's sad to see but I honestly don't know what else to do. He's on Lamb & Rice food . We can't afford allergy testing and if we find out it's inviromental & food, then what ? thank you.  

Answer
If you have a good vet, they would have put your pets on an RX flea control regardless of not seeing fleas.

Also if they suspect food allergy, a special RX diet should have been prescribed.

Topicals usually don't help. Many pets need systemic medication.

Get a second opinion :)