Sarcoptic and Demodex mites are two entirely different critters, but you definitely don't need a vet or toxic substances to get rid of either of them. The medicines used to treat them are harsh and often have hideous side effects. There are many safe, effective natural remedies out there to get ride of mange mites. We used something called Mite Avenge which was like a miracle. Many people use other cures.
Just do your homework and learn all your options. Question sources that say vets and chemicals are the only way. It's not that black and white.