Blisters are the most common trail injury.  They ruin many hikers day,  or worse spoil an entire trip.  Fortunately a little prevention and early attention to hot spots can usually stop a blister from forming.  Blisters are fluid-filled bumps that look like bubbles on the skin. They are caused by friction, a seam in your boot, a wrinkle in your sock, sweaty or wet socks , or an ill fitting boot.   Carrying a heavy pack, and hiking up hill increase the friction on the back of your heals, which makes the them the most common place people get blisters.

Prevention

The basis of preventing blisters is stopping friction.  This is accomplished by a combination of the following.

Hiking Boots

Your boots are the most important purchase you will make as a hiker. Buying the right hiking boots will save you from getting a nasty blister. More important than features or ratings, are how the boot fits your foot.  Each boot is made from an average foot model called a last.  Different manufacturers use different lasts.  Finding a boot that was made for a foot similar to yours will allow you to hike long days without blisters.  Your boot should fit like a snug glove. Find a breathable boot that provides good ventilation and reduces moisture.  A good boot is a balance between comfort, weight, and protection of your foot and ankle. Some stores offer a fake climbing slope to try out your boots. It is important that your foot doesn’t slide inside the boot while walking up or down hill. Your toes should have room to move, you should be able to wiggle them within the boot.

Break in Your Boots And Feet

Most modern hiking boots require very little break in time.  This still doesn’t mean that it is a good idea to tackle a major hike without first trying the boots out.  Start by wearing the boots around the house for several hours.   Pay attention to how your feet feel when you are walking around.  Do you feel any rubbing or discomfort anywhere on your feet?  Next take some walks around the neighborhood.  Finally go for a 1-2 to hour hike with a steep hill and a pack.  This should be enough to expose any major issues.  If you feel rubbing somewhere try to identify why.  Can you lace the boot differently? Can you lubricate or add moleskin to prevent that hot spot.  Would an insole or different sock make your boot fit better.  Your new boots will be a little stiff at first, which is fine. But if you notice significant pinching, rubbing or pain right off the bat, you may want to take the boots back and try a different style.

If you have purchased full leather boots you will likely need a full break in period I would say 5 different trips of 5 miles or so before taking on a big trip.

It is often said that you don’t really break in the boots you break in your feet.  There is some truth to this.  Getting your feet toughened up to the places where they are likely to rub helps reduce the discomfort.

Lacing Techniques

Properly lacing your boot can do a lot to prevent movement. Do yourself a favor and watch this video.  It is good.

Insoles

If your boot is close to fitting but is still causing some issues. You could try adding an after market insole.  Good ones run near $50 but they do make boots very comfortable.  They vary in how much volume they take, if your foot is moving around perhaps adding a high volume foot bed will help.  Some of them have a deeper heal cup which can help lock the heal in place.

Socks

A good sock is very important.  Wool hiking specific socks such as those by smartwool are designed to wick moisture, keep your foot at a comfortable temperature, and cushion your foot.   Colder temperatures call for a thicker sock.   A bigger sock takes up volume in your boot so make sure you try your hiking boots with the socks you intend to use on your trip.

IF YOU WEAR COTTON SOCKS YOU WILL GET BLISTERS! Cotton socks trap moisture and bunch up. Both of these are a recipe for a bad blister.

Some people swear by liner socks others believe they hurt more than they help. Personally I find them to help.   A liner sock is essentially a base layer for your foot.  They should be thin, fit very snugly, and be made of a moisture wicking material.  If your liner sock traps moisture or bunches it will just cause blisters.   REI Coolmax liners, and Ininji toe socks are the two liners I prefer.

When you put your socks on make sure that they are smooth with no wrinkles. Make sure that the heal sits in the right place.

Toughen Feet

If you have tough feet you will likely not experience discomfort or blisters.  Even the best fitting footwear will make your feet hurt after enought miles.  The solution lies in getting your feet tougher.   The most effective way to toughen your feet is to log lots of miles on the trail.   If that isn’t a possibility some of these tricks can help.

• Walk on pavement or concrete barefoot
• Soak your feet in a strong tea (note will cause discoloration)
• Use a product such as Tuf Foot 
• Use rubbing alcohol (this dries the foot and can cause cracking)

Trim Your Claws

Are your claws fearsome enough to scare away any predator you encounter on the trail?  Can you frontpoint up an icy slope with your middle toenails?  As impressive and useful as your talons may be, make sure they are well trimmed.  This will prevent shredding your socks, and more importantly your small toes can get rubbed raw by neighboring toenails.

Lubrication

Another common method of blister prevention is to lubricate the area that is rubbing.  Putting oil in your car lubricates the metal, reducing friction and thus wear.  In much the same way, adding lubrication to likely hot spots allows layers to slide smoothly stopping blisters from happening.   Many people just use petroleum jelly but there are several products made specifically for this purpose.  The main two I would recommend are Bandaid Blister Block, and Bodyglide.

Pre Treating

If you have an area on your foot that always develops a hot spot a few miles in, it is often better to pre treat with moleskin or ducttape.   The downside of this approach is that if your pretreatment works loose and bunches up it will just make things worse.  Additionally the adhesive in the pretreatment can cause the socks to bunch up.

My mountaineering boots always rub the back of my heals.   So before any major trip I put a strip of duct tape up the back of my heal, and then liberally apply body glide to the outside of the duct tape.  This seems to work well for me, and I rarely have issues.   I have had much less luck trying to pretreat problems on my toes caused by ill fitting boots.

Treatment

Preventing hotspots from forming is your primary defense against blisters.  If you follow the steps above hopefully you will not need the content in this section.  Still you must be prepared with the eqipment and knowledge to treat.

Early Treatment is key!! If you feel a hotspot developing, stop immediately and address the problem.  If you tough it out till the next break you will likely have  full on blister.

My favorite products for treating blisters / hotspots are

• Senco Second Skin 
• Dr sholes moleskin
• Duct tape
• Blister bandaids (these seal the blister and really stay put even in water)

This is a good article with more detail on treatment of blisters.  The basic goals are to clean the wound, and then cushion and protect so you can limp out of the woods.