In order to properly treat a ailment, One must first understand what they are first dealing with. 
   What are blisters? Blisters ; A small bubble on the skin filled with serum and caused by friction, burning, or other damage. Form swellings filled with air or fluid on some part of the body. It is  typically caused by forceful rubbing (friction), burning, freezing, chemical exposure or infection. Most blisters are filled with a clear fluid called serum or plasma.
However, blisters can be filled with 
blood (known as blood blisters) or with 
pus (if they become infected).
The word "blister" entered English in the 14th century. It came from 
the Middle Dutch "bluyster", and was a modification of the Old French 
"blostre" which meant a leprous nodule—a rise in the skin due to leprosy. Sometimes, the skin will blister when it comes into contact with a 
cosmetic, detergent, solvent or other chemical. This is known as contact dermatitis. Blisters can also develop as a result of an allergic reaction to an insect bite or sting. Some chemical warfare agents, known as blister agents or vesicants, cause large, painful blisters wherever they contact skin; an example is mustard gas.

Usually a Blister is A small, unbroken blister less
  than 
1 in. (2.5 cm) across, even a blood blister, will usually heal on its own. Preventing Blister's are now easier than ever. Ensure that shoes fit correctly, Protect the potential 'hot spots' by applying a second skin and / or taping , If you wear boots such as those required for mountain walking ensure
 all seams are flat inside the boot. Take care of the boots, do not 
leave them on radiators or near heaters. This may cause the leather to 
shrink and seams protrude.Keep feet as dry as possible. Wet shoes, boots and socks will cause blisters far quicker than dry ones. Wherever possible change socks regularly and use foot powder to help keep them dry. Break in new shoes gradually and put petroleum jelly or an adhesive 
bandage on areas that take the rub -- before the blister happens.

If your blister doesn't heal or is extremely painful, see a doctor. To  
prevent future blisters, you should not only switch (or pad) your shoes,
 but also keep your feet dry and powdered. Excess foot moisture promotes
 bacterial problems that can lead to peeling and blistering skin. Be 
especially sure to take these precautions during warm weather (because 
heat increases body perspiration and foot wetness) or if you are 
regularly in a place where your feet sweat and/or are exposed to wetness, such as a health club. Don't wear the same pair of shoes (or sneakers) every day.
Uncomfortable, unsupportive shoes -- if you walk around in them long
 enough -- will also eventually cause a burning sensation in the soles 
of your feet. Probably all experienced travelers have at one time or 
another paid this painful price; many now make their excursions in shoes
 chosen for comfort and support.