What is a backpack blister?
Backpack blisters are extremely painful skin lesions that develop where pressure, friction and sweat are at their worst. They tend to appear under rucksack straps and at the lower back where the bottom of the pack sits and repeatedly bounces.
They often start as chafing, rubbing or lowgrade irritation, then progress to a blister. With continued friction, the blister roof can tear away, leaving an open wound. Because these areas are out of sight, problems are easy to miss until the skin is already badly damaged or infected.
About me
I am an expedition podiatrist specialising in blister prevention and treatment. I have served on medical teams at the Marathon des Sables (MDS Legendary), Fire and Ice Ultra in Iceland, the London Marathon and the Great North Run. I am used to diagnosing complex overuse injuries and treating infections, sprains, pressure sores, chafing and a wide range of blister problems commonly seen at these events.
After I return home, I reflect on the issues I have seen and treated, then write about the problems that could have been prevented, so the next cohort of runners can learn from them.
How to prevent backpack blisters
Preparing for a selfsufficient ultramarathon often focuses on pack weight, which is important, but it is only part of the story. Pack fit, load distribution and skin preparation are just as crucial.
1. Get the weight and load right
- Aim to keep your pack between about 6–8 kg at the start of a desert or selfsufficient race; it will naturally get lighter as you eat through your food.
- Packs over 10 kg are much more likely to cause problems: the extra force through the straps and lower back increases bounce, pressure and shear stresses on the skin.
2. Train with your race pack – properly loaded
- Wear your pack for months before your event, not just on long runs but also for dog walks, commuting or shopping.
- Train with the exact weight and layout you plan to race with, so the skin and soft tissues on your shoulders and lower back are conditioned to the type of friction and pressure they will experience.
- Notice early where hotspots appear and address them in training, not on day one of a race.
3. Prioritise fit – especially for women
Pack fit is as individual as footwear. What works brilliantly for one person can be a disaster for another.
- Adjust the shoulder straps, sternum strap and hip belt so the load sits on the pelvis rather than hanging from the shoulders.
- Women often have additional challenges: shorter backs, different curves and bra straps can all add extra irritation points. A pack designed with women’s back length and shape in mind is usually worth the effort to find.
Why creams and powders are not enough
Antichafing creams and powders have their place, but the pressure and friction from a loaded backpack are usually too great for them to work on their own over many hours and days. They can reduce surface friction but will not compensate for:
- Poor fit or excessive weight.
- Straps digging in or bouncing.
- Wet, salty, sweaty skin under constant load.
They are best thought of as an adjunct to good pack fit, training and taping, not a standalone solution.
Using tape as prevention – getting it right
Some runners successfully use tape to prevent backpack blisters. It can work very well, but tape choice and skin sensitivity matter.
Choose skinfriendly tapes
If you have sensitive skin, the adhesive can make a big difference, especially in heat and with heavy sweating. In my own practice I tend to favour:
- KT Pro range of tapes
- Haplaband tape 5cm width
- Fixomull/Hypafixtype fixation tape
These are tapes I use in clinic frequently. Personally, I am allergic to zinc oxide tape and avoid it completely. Others do like it, but desert conditions are where hidden sensitivities tend to appear, and the last thing you need midrace is an allergic skin reaction under your pack straps.
How long can tape stay on?
Most goodquality tapes can stay on for several days. However, in extreme heat and constant sweating (for example, a full week at Marathon des Sables), even the “stickiest” tape will struggle to stay attached to skin on its own. That is where skin glue comes in.
Skin glue: making tape last in extreme conditions
For hot, multiday events, using a medical skin adhesive under tape can dramatically improve how long it stays in place.
- Apply a medicalgrade skin glue (such as SkinTac–type products) to clean, dry skin where the tape will go.
- Allow it to become tacky or dry as directed, then apply the tape smoothly without wrinkles.
Please avoid using compound tincture of benzoin (TBCo) if you are heading to extreme heat. It can work, but it has a higher tendency to cause allergic reactions when the skin barrier is already stressed by heat and sweat. Medical skin adhesives designed for longterm dressing fixation are generally kinder.
Use wider tape for better coverage
For backpack areas, wider tapes are particularly useful, for example:
- KT Pro Extreme WIDE tape (or similar wide elastic tape) across the lower back where sweat and waistband friction collect.
- Wide strips down the upper back and under the shoulder straps to spread pressure over a larger area.
You will almost always need help applying glue and tape to your back at events – it is not a DIY job. Medical teams are very used to doing this, and fellow competitors often help each other; it is part of the “family” feel of multiday ultras.
A clear “no”: duct tape on skin
Duct tape should never be used directly on skin. The adhesive is designed for metal and plastic, not for human tissue. It is:
- Extremely difficult and painful to remove.
- Likely to tear off superficial layers of skin.
- More likely to trap sweat and bacteria under an occlusive barrier.
Save duct tape for broken kit, poles and wing mirrors – not for your body. If you want to read more on this, I have already written a detailed blog:
When backpack blisters have already appeared
If your pack has already caused blisters or open wounds, the priority shifts to:
- Protecting the area from further friction and pressure.
- Reducing infection risk.
- Allowing healing while keeping you as functional as possible.
Dressing strategy
Depending on the size and depth of the wound, I would typically consider:
- Longer island dressings to cover linear strap areas.
- Foam dressings over larger, shallow wounds to provide cushioning and absorb shear forces.
- A suitable wound gel (for example, a Flaminaltype gel) under the dressing to support a moist healing environment.
- Securing everything with a reliable fixation tape such as Hypafix, taking care not to create new rub points at the edges.
At an event, always involve the medical team. These wounds are in awkward places to see and reach, and reducing the risk of infection is paramount. They can also advise whether antibiotics, rest or, in some cases, withdrawal from the race is the safest option.
Key takeaways
- Backpack blisters are preventable more often than they seem – but only if pack weight, fit, training and skin preparation are all addressed together.
- Tapes, creams and powders are tools, not magic fixes; they work best when combined with a realistic pack weight and a wellfitted, welltested setup.
- Once a blister has opened and become a wound, professional help and proper dressings are essential to keep you safe and, where possible, keep you moving.
Blisterhelp Marathon Des Sables Pilot Studies
About The Author
I’m Lindsey Ebbs, a podiatrist with more than three decades of clinical experience and a passion for working in the world’s toughest endurance events.
