There might be multiple reasons why your Yorkie’s skin has turned from normal whitish pink to irritated red/dry/flakey/rough/swelling on some spots. You may also notice your dog chewing parts of his coat intensively, which is also a sign of itchy skin problems. This is dangerous, because it can cause hair loss, infection and spread over time. To find the cure you have to detect the exact reasons causing sking problems, which sometimes may be not easy, and then apply proper measures.
One of the reasons causing skin problems is too much hair covering the dog’s skin due to too long haircut. The hair here is so dense that it obstructs the airflow. In this case it’s just about dog’s proportions in comparison to haircut, so just consider either brushing more often to provide the airflow, or making a short haircut for your Yorkie just to see if it’s the real cause for the problem.
Sometimes there might be just too much dead hair remains close to the dog’s skin, obstructing the airflow aswell. To get rid of this, brush Yorkie more often using a soft slicker brush. You need to adjust the intensity of your brushing untill you see the dead hair on the brush.
In this case grooming should be done every 3 days or so.
Improper bathing is a common reason for skin problems aswell. Some owners try to use human shampoo, which is dangerous, because it has different pH level, designed for humans and can cause problems to dog’s skin. A low quality dog shampoo may also cause irritation. The way you rinse out the shampoo is also important, because any soap suds are guaranteed to irritate the skin.
Use an oatmeal dog shampoo and be sure to rinse it out completely. You may also use a dog conditioner after the initial bathing(remember to rinse it out aswell!).
Also make sure the water you are using is not too hot for a Yorkie(you may feel okay about the temperature, but your dog may not), try making it a bit cooler just to compensate.
Allergies can cause skin problems aswell. It is somewhat hard to identify the real cause of allergy here. The most often reasons include: mold, dust, pollen, saliva of fleas. Fleas are especially hard to notice since their color may match with Yorkie’s coat. They can jump from one dog to another from a distance of 6 feet, and a single drop of their saliva is enough to cause skin irritation.
Other triggers for allergy may include food, cleanser and detergent components. A dog may get an allergy anytime during the life, so there’s really no “allergy-proof” solution for this.
Low oil content in your dog’s nutrition may also be the problem. You may simply feed Omega-3 capsule to your dog each day during 3 weeks. This oil helps against dry skin and has an anti-inflammation effect. Some people also add olive oil to the nutrition which has similar effects.