Blisters are usually caused by injury to the skin from friction and/or heat on the skin can create a tear between the upper layer of the skin (the epidermis) and the layers beneath. When this happens, the surface of the skin remains intact but is pushed outwards as serum collects in the newly created space between the layers. If your skin is rubbed for long enough, a blister will form. Blisters form more easily on moist skin and are more common in warm conditions. If you continue to walk, run or cycle with blisters, they will get worse.
As with most things, prevention is better than cure. The best way to prevent blisters is to keep your feet clean, make sure you have well-fitting comfortable boots or shoes, change your socks regularly, use good quality socks especially for longer distances. Blisters are more likely to develop on moist skin so splashing out on a good pair of moisture-absorbing socks can help prevent blisters and save a lot of pain in the long run.
Most blisters heal naturally and do not require medical attention. As new skin grows beneath the blister, your body will slowly reabsorb the fluid in the blister and the skin on top will dry and peel off. This normally takes three to seven days. The unbroken skin over a blister provides a natural barrier to infection. The skin should remain intact to avoid infection. Never pierce a blister with a needle. Allow it to break on its own once the skin underneath has healed.
Cover small blisters with a plaster (adhesive dressing). Larger blisters should be covered with a gauze pad or dressing that you can tape in place. If you have a blister that is painful or in a position that makes it likely to burst, cover it with a soft dressing to cushion and protect it. Change the dressing daily.
If a blister bursts, do not peel off the dead skin on top of the blister. Allow the fluid inside to drain, then cover the blister and the area around it with a dry, sterile dressing to protect it from infection until it heals. If a blister becomes infected, it needs to be treated with antibiotics.
Blisters are sometimes filled with blood (called blood blisters) or pus (if they become infected). A blood blister usually forms when a small blood vessel close to the surface of the skin ruptures (breaks) and blood leaks between the layers of skin. This can happen if the skin is crushed, pinched or tightly squeezed. Blood blisters are dark in colour and are often more painful than other blisters.
Leave blood blisters to heal naturally. If a blood blister bursts, keep the area clean and dry and protect it with a sterile dressing to prevent infection. Blood blisters are often painful. An ice pack applied to the area immediately after the injury can help relieve pain. Apply the ice pack for between 10 and 30 minutes. The ice should not touch your skin directly as this may cause a cold burn, so place a towel over the injured area before applying the ice.