Well unless your horse has app parents it is not app. I have a gray horse that when he started turning two he started to get these dark gray spots all over his skin and in certain areas it would discolor the hair that grew in that area also giving the appearance of spots. They were randomly all over his body, alot of people asked me while showing him if he was a few spot app. He isn't, I think it is just something in his graying that causes this.