Skin discharge or oozing from the skin is rarely straightforward, and there can be many different causes.
The most important thing you can do is pay attention to how the discharge presents; what it looks like, how it smells, if your dog is itchy, etc. All of this information is beyond helpful to your veterinarian.
Once your veterinarian determines if the discharge is fungal, bacterial, or allergic, they will be able to provide treatment in the form of oral medications, topical medications, diet, or medicated shampoo.
Don’t allow your dog to scratch or lick, no matter how sad they look at you with those puppy dog eyes. Fortunately, skin discharge is treatable, and finding the root cause of the problem will allow for prevention going forward.