If your horse has white plaque on the inside surface of his ears, don’t get too worried about it. Varying from white or non-pigmented, slightly raised to distinct “bunch of grape-like” lesions, this ear plaque is a type of wart (papillomatosis virus) that rarely causes problems, and treatment is usually unnecessary. While ear plaque typically doesn’t get worse, it usually doesn’t go away either. Contact your vet for a definitive diagnosis.