Every bushwalker will get a blister or three sometime in their life but it doesn't have to mean the end of walk.
A blister is when a layer of fluid that forms between the upper layers of your skin to protect the skin below, cushioning it from whatever damage is occurring and allowing the lower area to heal.
Causes: For walkers the likely cause of a blister is friction. This can be exacerbated by dirt; which causes friction, moisture; which softens the skin and can make seams or socks swell and rub, and heat.
Prevention: As usual, prevention is far better than any cure. The classic faux pas which will lead to blisters is not wearing in new boots. This is more likely to be a problem if the boot has a tougher exterior such as leather, but can cause problems in any boot. There is no quick fix when wearing in new boots, gradually increase the amount of time you spend in them and work up to the types of terrain you’ll be covering. This will ensure your foot is prepared for the tough grind ahead.
On the trail, if your feet get wet, clean and dry them as soon as practical, putting on a pair of dry socks if possible. Wearing two pairs of socks can reduce the friction between sock and shoe and wicking socks or foot powder will help reduce moisture for those with sweaty feet or in humid areas.
Finally, if you suspect you might have some problems, pre-emptively tape the areas concerned.
Cures: If you can feel a hot spot on your feet, stop immediately. Clean and dry the area, then apply anything which will reduce the heat and friction being applied. Sports strapping tape is cheap, lightweight and potentially useful for other things on the trail and so a good option. However blister band aids or even duct tape can suffice.
Lubricants such as petroleum jelly will bring immediate relief but can lose their effectiveness as they melt.
If a blister has developed and is hurting, you might consider draining the blister. Apply a sterilised needle to the side and base of the blister and allow it to drain. The Army has anecdotal stories of a piece of thread passed through the entrance and exit of the blister holes to act as a wick for draining, but don’t leave it in too long as this can also attract bacteria.
Don’t remove the dead skin as it will continue to help protect the new skin underneath. Try to keep it clean, give it air and reduce the pressure on the area as much as possible. Don’t pop blood blisters and if you see pus, it will need further treatment.