Just go to the veterinarian store, there are special drugs for dogs.
How to see if the dog is sick:
First look at the dog's eyes: whether the eye is dull, squinting, conjunctiva, sclera redness and swelling, the corners of the eyes attached to purulent eye droppings or dirt, etc.;
The second step to view the dog's nose: whether dry, scabs, cracks, runny nose, etc.;
The third step to view the dog's coat: whether the coat is rough and lusterless, itchy skin hair loss
The fourth step to observe the dog's behavior: whether to avoid light and fear of people, do not listen to the master's call, or in situ circles, wandering, or manic, up and down, etc.;
The fifth step to observe the dog's habits: living and living, habits have changed a lot.