No nasty comments please ...
stone bruises. It happens. Keep them soaking
Wet conditions where moisture, dirt and bacteria track up through tiny cracks in the hoof causing an infection. A stone or piece of wood gets trodden on and gets embedded in the foot. Cushing's disease as they are more prone to infections. If the horse has or has had laminitis as the laminae are stretched and things get in. Scrub the foot in hot salt water with the hoof pick brush, soak the foot in warm salt water if the horse will let you (obviously not hot enough to burn). Hot poultice the foot and bandage twice a day til the pus is all out, then for 3 days syringe some hydrogen peroxide (from chemist costs about 89p) Then spray some iodine on it for 3 days, that should kill the infection. If that doesn't work the farrier will need to look at it.
if it's been exceptionally rainy where you live or if the ground where your horse is turned out is chronically wet this can soften the hooves and increase the odds of your horse abscessing. i used to have a thoroughbred who would always graze in the part of the pasture that was constantly wet and he would abscess ALL THE TIME.
is it same foot if so, maybe infection never cleared up right. get vet or black smith to drain it and bath in salt water and fill with cut and heal cream, do this for few days. thats what i done with mine and never had problem since.
It could be a few things, even just bad luck. My first thought is moist conditions, my second is that I believe that Cushings makes horses more prone to abscesses, so it's just a thought.
It happend to my horse too, I just gave him foot bath with EPSOM salt and in 2 days, the absesses were gone! But I agree with one of the answer, just walking on a road with rocks can be the reason.
