Hi

My bitch is constenly itching esp her back, if you touch it gentle she twitches and wants to itch it

Noticed to day she is very dry skin and not sure why she is like this the other dogs do not present with this

There is no fleas present

Have you any ideas , ie food ,oils etc that may helpw

I couldnt work out from the picture which breed your dog was, does she have a thick coat? My old collie had a yeast infection on his back when we got him he was always trying to get us to scratch his back and was very itchy and flakey the vet said it was because he was kept outdoors and wet alot of the time before we had him she told us to rub some natural yogurt on his back on the itchy places and leave for a few hours then rinse him off and dry him through, it soon cleared up. It could be a yeast infection but i think you would know from the smell if it was that as it smells pretty bad too, or it could be a different skin condition or an allergy only thing you can really do is go to the vet and see what they say.

I suggest you have your vet do a skin scrape for any external parasites such as mites.
'Walking Dandruff' Cheyletiella sp is a common skin commensal on dogs and flares up from time to time especially in times of stress.
Eliminate things one at a time, firstly see your vet , then diet, environmental factors etc.