Foot blisters are one of the most common (and annoying) running injuries. Read on to find out what causes them, how to treat them and – most importantly – how to prevent them.

What causes blisters?

Blisters are basically pockets of skin filled with fluid. They form when the layers of the skin (dermis and epidermis) separate and fluid flows into the gap, causing pressure and swelling. You can also get a blood blister if blood flows into the gap between the layers of skin.

Blisters are caused by a combination of friction and moisture around the feet. That’s why they’re a problem for runners – your shoes rub against your feet as you run and sweat keeps the area moist.

How do I prevent them?

Thankfully, it is possible to avoid blisters! Try following these top tips:

• Buy good quality running footwear and get expert advice from a running shop about what shoes best fit your needs. Avoid shoes that press against the tops or sides of your toes, as well as shoes with a higher ankle counter, higher heal counter or unusually high instep.
• Don’t wear new shoes for a long run or race – wear a comfortable, worn-in pair instead.
• Invest in some sports socks, which are specially designed to draw moisture away from your feet. Just because some socks may have a sports label, it doesn’t mean they’re always suitable for running – so be sure to check. For example, cotton socks tend to absorb moisture and then go hard as the fabric dries, increasing the risk of blisters.
• Try to keep your feet dry while you’re training. If it’s easy to avoid a puddle or wet grass, for instance, then do so!
• Apply a drying agent like methylated spirit to areas of your feet that are prone to blistering, but avoid getting any on existing blisters as this can be very painful.

Is it a good idea to pop blisters?

The size and location of a blister determines whether you should pop it or not. Ideally, you should keep blisters intact, because while they’re closed they’re sterile and unlikely to get infected. However, if a blister is in a prominent place where it’s put under pressure or rubbed against, popping it is often the best option.

To pop a blister, lance the side of it with a clean needle and gently squeeze it to drain the fluid. It’s best to leave the top of the blister in place to keep out dirt and germs as it heals.

Put an antiseptic dressing over the blister and change this regularly. Make sure the dressing fits well and doesn’t move around when you’re wearing shoes.

How do I treat blisters?

Whether a blister has burst naturally or you’ve deliberately popped it, it’s best to follow the same advice of applying an antiseptic dressing and changing it regularly.

There’s a greater risk of infection from blood blisters, so be extra careful with them. Be sure to see your doctor if you’re concerned about a blister or if you experience severe inflammation, redness, pain or swelling.