Hi there and thanks for your question.
Not all cats can digest dairy products, but some can. Some vets will recommend small amounts of yogurt with active bacterial culture to help cats with diarrhea.
We don't recommend milk for cats because giving milk regularly can cause the pH of the urine to go up and predispose them to getting bladder stones.
I hope this information helps! If you have more questions regarding this problem, just hit reply. If I am online I will respond right away. Otherwise I will respond as soon as I come online again. Or, if my answer is sufficient, then please hit accept. Thanks!
The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would highly advise contacting your regular veterinarian.