I was interviewed over the weekend about "quick cures" for blisters that arise from shoes. As I explained to the reporter, blisters are a result of friction from your skin against a surface. The scenario was what to do if you developed a blister while on your way to work and had no other shoes to change into. It was ironic, because last week, I had a similar problem. I was going to an out of town meeting and only had the shoes I was wearing and developed a blister while at the airport on my way there!
Blisters can be caused by straps that lay across the toes (as in my case) or from shoes that don't fit well. Shoes that are too big and cause irritation from the foot moving around in the shoe, or from parts of the shoe that are too tight. Your body tries to protect itself from the irritation by producing fluid as a cushion that collects under the skin.
The best way to protect a small blister while you need to continue wearing those same shoes is to apply something that conforms to the toe to prevent further friction.
I like to carry a self adhesive 1 inch bandage with me at all times. One name brand is Coban. You just wrap it around the affected toe.
You can easily keep a small piece of this in your wallet and it will be there ready to use in a toe emergency!