A blister occurs when a tear happens between the third and the fourth layer of the epidermis (outer layer of the skin). The tear opens and fills with fluid from the capillaries below and hence the blister is formed, blister development time can be up to 2 hours but also can be much quicker than that.
The tear in the skin is due to repeated SHEAR stresses caused by friction, bone movement, heat, moisture and pressure applied to the skin.
Moisture is when the skin gets wet either by being in water or sweating, this then increases the co-efficient of friction, in English, a bit like when you spit on your hands to get a better grip, this increases friction. So we know that when feet are wet they will get more grip with the shoes and socks, increasing the friction which then in turn increases the shear of the skin increasing the chance of blisters.
Heat doesn’t actually cause blisters but when the feet get warmer they sweat, which means more moisture, more friction, and more chance of blisters.
Bone movement- every step you make the bones will move in the feet, which is perfectly normal but it is when the outer layer of the skin remains stationary then the soft tissues in between then stretch and distort. So when the sock sticks to the moist skin and then the shoe and the bones in the foot are still moving, then blisters are formed by the shear applied to that particular area of soft tissue.
Pressure- means forces that are applied to the foot, either downward force by the body, or an upward force from the ground (GRF). Carrying a 30kg back pack will increase the pressure down into and through the foot, whereas different types of surfaces that you walk on will exert an upward force (eg concrete will exert a greater force than sand or grass). If footwear is too tight or poorly fitted, it will exert pressure on the foot and then cause blisters.
Skin resilience- Skin is very resilient but when it is exposed to repeated stressors that it is not used to, it eventually breaks down and the healing process cannot keep up with the repeated trauma and you get blisters on your blisters! This resilience of the skin can be improved therefore decreasing the stressors applied to the skin.
So a blister formation is not due to just one cause but many, which is why a podiatrist can work out which one of these causes is creating your blisters and then help you to treat and prevent them.
Some people are blister prone, ie the shear strength of their skin is less than others. No matter what they do they will struggle with blisters. However for others, preparation is key, they have worn the right fitting footwear, correct socks and taken the precautionary measures to remain blister free.
Blisters can take up to 6 weeks to heal, which creates massive problems for people participating in sporting activities that last for several days at a time. Blisters can be formed on the first day and then the completion of an event is unlikely. The fear of getting Blisters can for some prevent them carrying on with their favourite sport or leisure activity and for those who like fashion shoes, a night out in your favourite shoes can be painful experience for the following 2 weeks in your work or casual shoes. They are very painful!!
Blisters affect 54% of backpackers to 64% of long distance hikers, incidence in marathons are up to 39% affected. Ultramarathon multistage runners suffer 76% to 100%.
Military personnel struggle with 48%-65% blister formation after short marches and 33% after a 12 month deployment. 84% of Cellulitis (Bacterial infection in the skin which spreads rapidly) in Military recruits is caused by blisters, this causes an average loss of 8 training days per recruit!
These statistics are huge, if these results had been recorded as any other injuries, something would have been done about it but most people tend to regard blisters as an acceptable part of an active lifestyle and they just don’t have to be.
Hotspot is when the skin starts to feel a little warmer than the surrounding skin and it may start to sting a bit, this is the warning stage and time to address it to prevent a fully formed blister.
Bubble Blister- the hotspot has progressed, the tear in the skin has been formed and a fluid filled bubble on the skin that most will recognise as a blister is now visible.
Roof torn- this has progressed from the intact blister and the roof or the top of the blister has a tear and the fluid has leaked out, so it is no longer looks like a bubble on the skin.
the tear has now is so big that it has completely removed the roof of the blister and it is now, essentially an open wound and needs to be treated as one.
The roof has come off the blister and the open wound has become infected by a bacterial infection, this wound needs to be immediately treated medically.
It is very important to treat each Blister stage with the right products, otherwise it could make the blister worse. Recognising when a blister is infected is so important in saving your foot let alone finishing your race or walk. Prevention is really the best form of treatment, if you know you get blisters or suspect you might, then wearing the correct footwear, taping, socks, using the right products is the key to success and completion of any planned event. There are so many products on the market, making it very difficult to choose the right one, a lot promise a great deal but if it is the wrong product for you or addressing the wrong stage of a blister then it will fail to succeed.
As podiatrists, we deal with feet problems all the time, we are the most experienced medical professionals in dealing with foot related issues.
You may see Podiatrists as part of a team in departments of Dermatology, Diabetes, Paediatrics, Musculoskeletal (Biomechanics), Peripheral arterial disease (PAD), Rheumatology and Rehabilitation, Forensics, Podiatric Surgery as well as Podiatrists dealing with routine general podiatry in Hospitals, GP surgeries and private practice. As a profession we treat a lot of problems associated with the lower limb, which is why we are well qualified to help sort out your blisters.