fleas
First of all don't let your dog play with a sick dog. Tell the owner of the sick dog to take it into a Veterinarian. If your dog is losing large amounts of hair or has bald spots on his coat, take him into your Veterinarian to be checked out for such things as demodex or sarcoptic mange mites or other issues. Losing small amounts of hair is normal as they are shedding. Make sure you have your dog on a good brand name of dog food.
Is you dog showing signs of a pot belly or eating more than usual? Losing hair is a sign of cushings disease
I used Epi-Smoothe on my dog. She has some spots where her fur is falling out
A dog's hair changes color over time due to a natural process called graying, which is caused by a decrease in pigment-producing cells in the hair follicles as the dog ages. This results in the hair gradually losing its original color and turning gray or white.
Hair loss on a dog's feet can be caused by various reasons, including allergies, infections, parasites, or autoimmune diseases. It is important to consult a veterinarian to determine the specific cause and appropriate treatment for your dog's condition.
Look up Mange... and consult a Veterinarian.
There are many reasons that your dog is having diarrhea and losing hair. Take your dog into your Veterinarian to have a check up. Bring in a small sample of your pet's feces too so the Vet can check it for internal parasites or signs of blood. Don't try to diagnose your dog yourself, take to your Vet. Make sure you are feeding your dog a good name dog food and not some cheap store brand food.
If a dog (any dog) is losing hair in big enough patches to see his bare skin where he has lost it, he probably has mange, and should be seen by a vet. There are other causes too,but mange is the first thing the vet will suspect. Take him to the vet.
Your dog probably has allergy's and is gnawing on his feet to try to stop the itch or your dog is getting old and has callus from so much use.
It's hard to tell for sure what is wrong with your dog if he is losing weight and scratching his hair off. It could be related to a thyroid problem or he might be allergic to the food you are feeding him. He also could be having an allergic reaction to fleas or to something else in his environment. Take him to a veterinarian to get him treated.
Either it has mange or an infection, or possibly even fleas, I'd get it checked out soon, as mange can be deadly.
You cannot make dog hair. You must obtain dog hair from a dog.