Skin issues and allergies

I have a 3 year old female border collie and I have been having a nightmare with her skin. She has been to the vet many many times and tried many medications to no avail. Can any one advice please

Hi - and thankyou for sending the pictures.  Of the questions I get asked along the lines of 'my vets' treatment isn't working,' more of them are about skin disease than any other topic.  I suspect that this is because a) skin is a superficial thing, so our perception is that it should be easy to treat and b) if the underlying cause does not go away, it tends to come back.   Underlying causes of skin disease tend to be:  1) pain - either at that place, or in the abdomen (because the leg might just be an easier place to reach than the abdomen).  2) parasites eg fleas or mites, which can take time to rule out and commitment to stay on top of.  3) viral rashes, cancer etc 4) foreign bodies under the skin 5) allergy.  Which is notoriously difficult to pin-point.  Soooo......

Ruling out various different causes of skin disease can take time, and repeated vet-visits.   Many vets give symptomatic treatment ie designed to stop and licking and to protect the skin's surface, so keeping the patient comfortable while investigations are carried out.  Typically the patient gets better for a while and owners understandably feel that a recheck would be superfluous at that time and do not return, so it can take some time to do tests to establish the underlying cause - and depending on the cause, the first round of tests (eg ruling out parasites) is unhelpful and more are required.  Vets usually take a look at the patient, lifestyle and history before deciding what the most likely causes are, and what to rule out first.

*to stop any licking*

So....  In order to get the best out of your vet, we would encourage the following process of questioning:  1) What are the possible causes of this problem?   Have you ruled anything out yet?    2) how could we diagnose this with certainty?   3) Is that process worth persuing practically?  4) what else can we be doing, to try and keep our collie comfortable in the meantime?   (Examples might include regular rinses eg to remove allergens from feet / abdomen after going out)  5) So you're going to do X, which will either show outcome 1 or 2.   What will we do if we get outcome 1?  What if we get outcome 2? Please remember that skin disease is difficult and complex  to diagnose.  Where finances are constrained (which is most cases), we would reccommend discussing this with the vet in advance so that they are aware of where best to use the money.   I hope that something there is useful.

Please note that these answers are assuming that the lesion is being licked / worried it. If not, the process is the same but the possible differentials might be very different.