Blisters are the bane of many runners existence. Whether it’s a 5k race or a 100 mile ultra-marathon, blisters can cause significant discomfort and lead to poor performance. Blisters represent up to 70% of medical visits in ultra-marathons. Therefor, blister prevention is key to performance on race day.
How do blisters form?
Blisters are a friction injury, usually caused by skin rubbing against socks or shoes. Simply, as the external surface (sock or shoe) moves across the skin, a shear force occurs. Repetition of this force with each step damages the skin and causes blisters to form.
Risk factors for blister formation
- Skin characteristics: Callous formation can increase shear forces which increase risk of blister formation. Blisters under a callous can be particularly difficult to manage as they are usually deep to the callous and can be difficult to find when attempting to drain.
- Socks: Moisture wicking socks are essential. Friction is lowest when skin is very dry or very wet. Moist conditions significantly increase friction and risk of blisters. Furthermore, particles such as dirt and sand that collect in socks can increase risk of blisters.
- Shoes: There is no research data showing particular shoes or orthotics can increase or decrease risk of blister formation. However, shoes that are too small or too big can increase risk of blisters.
- Lubricants and Anti-perspirants: Lubricants can decrease friction when applied initially. However, over time they can increase skin moisture which increases risk of blisters. Anti-perspirants can reduce skin moisture and reduce risk of blisters. Unfortunately they often cause skin irritation which limits their benefit.
- Powders: Powders such as baby powder can in theory reduce skin moisture which should reduce risk of blisters.
- Taping: The application of paper tape can reduce risk of blisters by up to 40% (Lipman et al., 2016). Taping the whole foot or using small circles on hot spots can work. Ensure the tape does not have any edges that rub against your skin, as these edges can become points of friction.
- Sock Type: Moisture wicking socks are essential for all runners. Some sock companies claim to have extra blister prevention properties (See here at Wild Earth). Ensure you do not run in moisture absorbing material such as cotton.
- Gaiters/change socks: For ultra-marathons, either change socks at checkpoints or use gaiters to prevent sand and dirt build up in your socks and shoes.
- Foot Care: Remove any callouses as they appear. Also ensure you keep your toenails short, to avoid between toe blisters.
How to treat blisters on race day
Preventing blisters is ideal. However, it’s impossible to prevent blisters 100% of the time. Below we lay out a step by step guide to managing blisters on race day.
- Step 1 – Prepare the skin surface: Clean the surface of the skin with a dry cloth and then with an alcohol swab. Ensure the needle or safety pin in cleaned with an alcohol swab prior to use.
- Step 2 – Drain the blister: Puncture the blister once or twice with a sterile needle at the end of the blister. This will allow the pressure of the foot to squeeze out any excess fluid as you run. Then cover the blister with paper tape or a specialised bandaid that covers the entire blister.
- Step 3 – Taping: Thin paper and adhesive tape can be applied over the effected area to provide extra protection. Any tape used for blister prevention should be free of wrinkles, to avoid further hot spots.
If a blister is already “de-roofed”, trim the remaining skin with sterile scissors. Then apply a blister bandaid or paper tape circles over the entire blister area including borders, and then apply a final layer of adhesive tape as above.
Blister management kit for ultra marathons
For ultra marathons, having a small zip-lock bag with the below items will help you manage blisters on the run.
- Safety Pin for draining blisters
- Alcohol swab x 2
- 3-4 x pre-cut paper tape circles to cover blisters
- 3-4 x pre-cut adhesive sports tape strips with rounded edges to cover entire blister and surrounding area. Different sizes to account for between toe, underfoot and heel blisters
Lipman GS, Sharp LJ, Christensen M, Phillips C, DiTullio A, Dalton A, Ng P, Shangkuan J, Shea K, Krabak BJ. Paper tape prevents foot blisters: a randomized prevention trial assessing paper tape in endurance distances II (Pre-TAPED II). Clin J Sport Med 2016;26(5):362-8