Unfortunately, due to the unpredictable nature of proud flesh and lack of scientific data on how to treat this condition there is no set time frame. The treatment can vary from weeks to months before symptoms begin to improve.
How long it takes for proud flesh in horses to resolve will depend on many factors including: location and size of the ulcer, age and general health of the horse, and how often the treatment is applied.
Proud flesh will not resolve without attention and treatment and can lead to debilitating injuries if left alone. If you haven't been able to get rid of it yourself, please ask your veterinarian for help before any permanent damage occurs.
In addition, make sure your farrier knows how to work with the horse on a daily basis so they can catch any new problems before they become an issue. But if proud flesh seems like it's taking more than 3-4 weeks to heal, you should contact your veterinarian immediately.