Infection around dogs mouth can anyone help what it is and how it can b treated

There is infection around the mouth of this stray dog

Hello - I'm afraid that the fact is, that if the cause of dermatitis ("inflamed skin" - thats a description of a symptom, not a diagnosis) could be seen from a photo at a distance, and then a correct remedy looked up in a book or online, then there would be no need for vets (or doctors for that matter).  The fact is, that many diseases look very similar on the outside.  This one could be caused by parasites such as mites, by autoimmune disease, allergy, trauma eg self trauma in a response to toothache, or possibly related to neuropathy or even (but very rarely) cancers such as lymphoma.  I cannot say that there is an infection from here; I have seen many things looking like this that have only been 'infected' by the bacteria existing on the skin normally; many evil-looking skin "infections" turn out not to need antibiotics.  So, the best thing to do with this would be to let your vet examine the skin, to try to figure out the underlying cause and treat that.

Having reread you question, I understand that this dog is a stray.  I wonder whether, where you are, there are veterinary charities that can take the patient in, do necessary tests and provide treatment?  This varies from country to country and more provision is badly needed everywhere.  I'm sorry not to be more helpful in this situation, but the cause of the signs makes a massive difference to the treatment needed.  Wishing you and the dog all the best of luck.