Hi and WELCOME to YT

! Glad you found us.
Well, unfortunately, you have a breed who is very prone to allergies and/or the skin issues that go with it. If there are red patches on the tummy, there is a very, very good chance it's an infection called pyoderma - this is staph intermedius. The only way to get rid of it is via a prescription from your vet; the standard for treating pyoderma is Simplicef x 30days (yep, 30 days!). So, I'd take your kiddo to the vet and the vet can do a skin scraping, look at it under scope, and see if there is bacterial overgrowth.
Is he itching only on his tummy? Does he chew or lick his paws? Checked for fleas?