If your horse's hooves seem to be looking worse than usual this summer, it might just be because of the change of season and environment. In summer, soles and frogs sometimes start peeling and flaking due to dry weather and because of footing that is harder and drier.
Equine hooves typically get plenty of moisture in the spring. As a result, the horn that emerges is very pliant and relatively soft. In the summer, drier conditions stimulate the growth of much harder, denser horn. The zone between the soft and hard growth eventually causes the frogs and soles to crack and peel.
The condition is temporary, and regular trimming will prevent it from causing your horse any trouble.
If your horse becomes lame or his hooves develop a foul odor indicative of thrush, consult your veterinarian.