What could be wrong with my terriers mouth

Hi my 2 year old parson terrier has developed a red rash and swelling all round her mouth and little sores too.
It doesn't seem to be bothering her at all and she isn't rubbing or scratching at it.

I took her to the vets on good friday and to say the least I was disappointed. The vet never even touched her to examine her mouth, she just said she will prescribe hibiscrub to bathe her mouth with and some tablets called prednicare. Then charged us £75 for a less than 2 minute consultation.
I know it has been less than a week but it isn't getting any better at all (looks worse if anything).

I will take her back to the vets but will see a different one next time, I wondered if anybody has any ideas as to what could be causing it? I haven't changed her diet or anything. The vet wasn't interested in what could be causing it but surely if we dont find out and try to eliminate it then she will always have it!
(This vet is new, the one we always saw left the practice last month)

Do you feed dry food? If so freeze it overnight. Make sure thoroughly defrosted next day before feeding. Sounds like she may have storage mite allergy, theyre present in all dry foods & freezing only way to kill

Could also be allergy some type - think of it, when investigating dogs head/ nose goes first & wee terriers like to explore. Think about where you walk, have you out any new plants in garden recently, used any new household products etc

Other possibility is acne which some dogs can be prone too.

Hi cld she have been stung,she will probably need an Antihistimine injection not sure if thats the correct word or spelling,but my dogs are always poking there nose into something or other,and if they get bitten,get given an injection and they are right as rain crystalgirl

We had a similar problem with our late Benny, it was his sloppy eating habits made the area round his mouth dirty causing rashes spots and soreness. Only real way to stop it was wash his face after he had eaten.

What an annoyance with the vet. I wouldn't have left until I got my monies worth. Hopefully you can see a different one soon.

It's hard to say what it could be, especially without seeing it. I wonder if it could be some sort of bacterial infection. Are the little sores oozing?

Thank you for the replies. Velvetboxers, i will certainly start freezing her food to be on the safe side. Nothing new with regards to cleaning products or plants.

Timber, the sores are not oozing, they are just scabby.
Still 5 days left on the tablets so I will see how she is then but I certainly will be seeing a different vet if it isn't any better and demanding further tests etc to find out the cause