What is this on my dog?

I can’t figure out what this is on my dog and I’m not currently in a position to go to the vet so I’m asking here first. Can you let me know what it is and if it’s serious? Thank you!

Hello!  I think i'm looking at patchy hairloss (please let me know if I'm seeing this wrong). It could be ringworm, which is a superficial fungal infection and can be caught by people; it could also be demodex, a mite that multiplies generally in the hair follicles, which can thereby cause the hair to fall out.  Other mites, tunours and so on are also possible. Either one of my main two differentials merits treatment; first, to clear up the problem and stop it spreading but secondly, because both tend to come about secondarily to some drop in the immune system, which may also be significant.   Its worthwhile getting this looked at and finding out whats going on.

Sorry - that was rather rambling.  Here it is simply:  from what i can see here, there are several possibilities including 1) demodex mites (mites that already live in the hair follicles in normal dogs. The immune system normally keeps their numbers in check.  However, if a dogs' immunity has taken a sudden huge drop in efficiency, demodex can multiply causing obvious spots of hair loss.  The drop in immunity is often something that needs to be addressed.) 2. Ringworm. This is also more likely to manifest in animals that already have challenges to their immune system ie the very young, very old and the ill.  However- it can spread to people, so avoid touching / contact with immunocompromised people until it has been ruled out.  This is another good reason for seeing a vet early. 4. Other parasites 5.  Allergy 6.  Cancerous change 7.  Exogenous markings - which cannot be ruled out from a photo. Im afraid that we would therefore suggest seeing a vet sooner rather than later.