i only get blisters on my left foot. my shoes fit fine. they are laways in the arch of my foot or near my big toe. what are they

• Heat, moisture and friction.
• Friction forces caused by inappropriate shoes or socks.
• Fungal infections of the skin.
• Allergic reactions or burns.
• Excessive foot perspiration.

Some ways to prevent blisters are:

• Keep feet as dry as possible.
  • Wearing wet shoes, boots and socks will increase your chance of developing blisters.
• Change socks regularly.
• Use foot powder to help keep your feet dry.

Treatments for Foot Blisters

If the blister has not "popped," leave it alone. Most of the time, the blister will reabsorb and heal on its own.

Not sure how old this question is, but I noticed the only response didn't answer your question at all.  There are two possible reasons to get blisters only on one foot:

1)  Most likely, it has to do with the way you run or walk.  Most of us have a dominant leg/foot, just as we have a dominant arm/hand, and there is a natural tendency to stay slightly more centered over your dominant foot, assigning it more load and control.  Depending on how much we favor one foot over the other when we walk or run, it causes significant differences in the way each foot interacts with the ground and with its shoe.

2)  A less likely reason could be your shoes.  Even machine-made shoes have imperfections all over them, including on the insoles.  If you get the same blisters no matter what shoes you're wearing, however, then this is probably not your problem.