Summarize this article in one sentence.
Blisters occur when something rubs against the skin and irritates it. There are a number of causes for blisters. These include:  Friction: This is generally intense friction over a short period of time. Corns and calluses develop from longer-term rubbing. Burns: Any source of intense heat from flames, steam, the sun, or hot surfaces can result in a blister Cold: Blisters can result from intense cold. Irritants or Allergens: The reaction of the skin to various chemical irritants or allergens can result in blistering. Drug reactions: There are a wide variety of drugs which can cause skin reactions, including blisters. Diseases and Infections: There are autoimmune diseases where the immune system reacts against components of the skin that can result in blisters. These all require medical attention. These disorders include pemphigus, bullous pemphigoid, and dermatitis herpetiformis. Infections with viruses, such as chickenpox, shingles, and cold sores, or bacteria can also result in blistering Genetics: Certain rare genetic disorders result in widespread blistering. Insect bites: Some insect and spider bites result in blisters. Most blisters are minor and will go away on their own. However, there are a few reasons why you should go to the doctor with a blister.  Go to the doctor if your blister is infected. The blister will have yellow or green pus in it if it is infected. It may also be extremely painful, red, and hot. See your doctor if the blisters are causing you severe pain. Get checked out by a doctor if your blisters keep coming back. You should also get checked out if your blisters are in odd places, like eyelids and your mouth. See your doctor if severe blisters are received from sunburns, burns, scalds, or allergic reactions. You should try to prevent any blisters from happening in the first place. To help prevent blisters on your feet, only wear properly fitting shoes or socks, shoes, and insoles marketed to help prevent blisters. You may also consider moisture-wicking socks.  Place moleskin on places in your shoes to rub against your skin or put powder inside your shoes to absorb moisture. Wear gloves to help prevent blisters from working or when handling cold or hot objects.

Summary:
Learn the causes of blisters. Know when to see a doctor. Prevent blisters from occurring.