I would not class this as an emergency but I would have a full thyroid panel run when you can get there to do it. Moist feeling skin in the underarm area always screams thyroid to me as that is one of the first areas to show symptoms, as well as the groin and under the tail.
Also- skin is one great big excretory organ. It literally discharges toxins and other undesirable substances that have found their way into your dogs system.
So my first thought would be to scrutinize what the dog is eating. Look at every morsel and every treat, read every label and be very consistent about not allowing artificial ingredients get by you.
What is the dogs primary food now?