Heel blisters are most often caused by shoes that do not fit properly. Shoes that are too tight can cause hot spots in various areas of the foot, and shoes that are too loose can rub in all directions on the heel, causing blisters. To avoid blisters, you should always choose a pair of shoes that fit snugly but not too tightly, and if you walk, run, or otherwise move around throughout the day, changing socks frequently can help prevent blisters throughout the foot. Replacing socks once they are worn out or too thin can also help prevent hot spots and blisters throughout the foot.
When a shoe is too loose, the heel of the shoe can move up and down as you walk, causing the fabric of the shoe and your sock to rub against the skin of the heel. Heel blisters often follow. To prevent such rubbing, you can either replace the worn or poorly fitting shoes with a better fitting pair, or you can add heel pads to your shoes. Heel pads add material between the shoe and the heel to essentially cut down the gap, preventing excess movement. Be sure to tie the laces of the shoe tightly as well to prevent excess movement.
Even if a shoe fits well, blisters are possible. As the foot sweats, friction increases between the foot, sock, and heel of the shoe, which can lead to hot spots or heel blisters. To avoid blisters in this situation, you should be sure to change your socks frequently throughout the day, and if possible, change shoes at least once throughout the day to allow the insoles to dry out. The drier you can keep your foot throughout the day, the less likely you are to get hot spots and blisters.
Your walking motion may also be the cause of heel blisters. People who walk heel-heavy — that is, they land heavily on the heel when walking forward — are susceptible to blisters on the heel because the impact of the walking motion can cause movement inside the shoe, even if the shoe is on tightly. The solution to this problem is not necessarily an easy one, and it may involve changing the way you walk. A walking gait adjustment can help alleviate other types of pain as well, so if your heel blisters are accompanied by frequent back pain or leg pain, a gait correction may be in order. Consult a doctor or other professional for such advice.