Choco Pie skin itch, ticks??

Choco Pie been scratching her ears for 2 weeks already. Yesterday I found a tick behind her ear, very small but still alive. I was so scared. We take her to the vet in Bang Kapi that same night, and the doctor said it is not only tick, maybe allergy too. The doctor checks her skin and blood, very long time. The result came out this morning, kidneys are ok na ka, but she needs special food for the skin and medicine for 1 month. I cannot believe the cost, 3000 baht for one visit. I have 2 dog at home and Bonbon did not scratch at all, so I think it is only Choco Pie. She is the one who eats grass in front of the soi every evening. I told her many times to stop. Now I put the anti tick drop every month and I wash her bed with hot water. Also I bought a steel bowl, the plastic might be bad for allergy. Okay will update.