yaya skin problem 2 month long

Yaya is my first dog and I dont know much about dog skin. For 2 month he is scratching all the time, especially at night, his ear and belly turn red. I think is just allergy from the food so I change food 2 time but still same. Last week we take him to vet near Khlong Toei. The vet check his skin and see some tick under his neck, very small, we almost miss it. She say ticks can cause the itch and also check if there is infection. Give him medicine to kill tick plus anti-itch for 1 week. Then she ask for blood test because the scratching is very bad and she worry about kidney and liver. I was very worry, I think maybe my dog is very sick. Result came back 2 day later. Kidney normal, liver normal, a little bit low on something but vet say not serious. So now the plan is tick prevention every month, bath with the special shampoo once a week, and no more chicken treat for now because maybe he is allergic. Yaya is happy with fish treat instead, he eat it so fast. I think the bad part is I was thinking about the price too much at the start. But after the blood test I feel better. Dogs cannot talk so we must watch them very carefully na krub. Also the condo juristic office said I cannot keep him in the common area too long because other owners complain about the smell. Ok I understand, I bring him down only in the morning now.