I had taken him to the vet in the past for this. Actually went to two vets.
First, he went on some orally antibiotics and anti allergic meds. That time he had some skin issues on his hind legs.
Next, I took him to another vet ( a clinic with multiple docs), he said that there was no need to worry, it was due his immunity being low, since he had been recently vaccinated. Said it was folliculitis / superficial bacterial dermatitis and prescribed cetrizine for a week.
Again when we went to the clinic, they took a skin scrape and a blood smear. He had a bacterial infection, so an antibiotic cream was prescribed. (During this time the spots where he had lost his hair, were red and had formed pustules.)
On a follow up visit, the vet discontinued all antibiotics and prescribed cetrizine for 2 weeks. This was in late August. Told us not to worry and said that it would clear off when he matures.
Later, I gave him some natural tabs for skin infections; his skin issues on his hind legs cleared off and hasnāt come back.
As of now, there are no pustules. Just dry flakey skin and his hair is falling quite a lot.