Flares can be the result of overgrowth or imbalance. Flared hooves tend to have flatter soles. This is due to the descent of the coffin bone as the attachments to the hoof wall have been compromised. You will see on the sole side of the hoof the white line will be blackened and stretched in response to flares. Flaring must be reduced immediately to stop further destruction of the attachments. Applying the mustang roll to the edge of the sole is necessary to stop the flare. Frequent trims are needed so that the excess growth and flaring can be brought under control. Once the white line is tightened up, you will be able to have less frequent trims.
Flares are supposed to happen when the walls become too long. If they didn't flare and subsequently chip off our horses would become taller (like having stilts). However, domesticated horses shouldn't be allowed to get this long even if this is what is supposed to happen. Horses in the wild wear off their hooves to be consistently short. Flaring doesn't occur in the wild.
Experiment: If you suspect flaring.... take a straight edge from the coronet band perpedicular to the ground next to the hoof, either on the toe or quarter. If you see daylight (a concave area) between the straight edge and the hoof wall, you have flare. A note on this; flare can start up as high as the coronary band and make this little test difficult to determine if there is flare. Consulting with a hoof specialist (farrier or trimmer) will help you determine if your horse has flare.
The horse was given all these great structures; hoof wall, frog, bars, and sole to support the horse. Horses were not designed to hang on the hoof walls over shoes. This creates large amounts of stress on the internal structures and weakening the lamellar attachments. They will never grow a solid, well attached wall void of flares or cracks as long as they are peripherally loading either in shoes or with overgrown hooves. The whole hoof is designed to bear weight and aid in shock absorption. Shock absorption will not be effective if we are suspending the hoof by the walls. The increased load on the walls can lead to breakdown of hoof function and can result in flares.
Nutrition must also be addressed when treating flares. The horse must have the essential nutrients to grow a healthy hoof from the coronet band down and from the coffin bone out. If the diet is lacking the horse will not be able to make good lamellar connections that support the coffin bone and eliminate flares.