Interdigital cysts are fluid filled, swollen sacs between the toes, usually on the front feet. The area is sore and painful. The dog will lick or bite at the area trying to break the cyst to relieve the pressure. It can be treated in several ways.
First, you can use a tweezers to remove any ingrown hairs from the underside of the cyst. Then apply pressure to the cyst to expel any fluid you can. This will usually work quickly. If it doesn't, try bathing the foot several times a day in an Epsom salt solution until the swelling bursts. If the area is red and swollen, use a cold water solution; once the redness disappears, use a hot water solution. An antibiotic ointment, like Panalog, placed between the toes helps to prevent infection once it bursts. In severe cases, your Vet may need to inject a cortisone-related drug to reduce swelling or to cut the cyst to permit it to drain.