A blister is a small pocket of fluid within the upper layers of the skin, typically caused by forceful rubbing (friction), burning, freezing, chemical exposure or infection. Most blisters are filled with a clear fluid called serum (Serum is the part of the blood that remains after red blood cells and clotting agents have been removed.)or plasma (aka, "blister water"). However, blisters can be filled with blood (known as blood blisters) or with pus (if they become infected). A blister usually forms because the outer layer of the skin has been damaged. Fluid collects under the damaged layer of skin, cushioning the tissue underneath. This protects the tissue from further damage and allows it to heal.

The word "blister" entered English in the 14th century. It came from the Middle Dutch "bluyster", and was a modification of the Old French "blostre" which meant a leprous nodule -- a rise in the skin due to leprosy.

Blisters, of the kind that occur due to rubbing by shoes, are best dealt with by covering with a gauze that has had a few drops of Lavender oil sprinkled on it. If the blister is large, it may be more comfortable to puncture it with a thoroughly sterilized needle, and then apply neat Lavender oil and a gauze covering. Oil of Myrrh added in equal proportions to the Lavender is valuable if the blister remains very damp, and oil of Benzoin can be used after initial treatment with Lavender, to help the skin heal.

Do not cover the blister with a plaster that lets in little or no air, but anchor a gauze dressing in place with plaster strips so that the skin can 'breathe' and leave off shoes and socks for as much of each day as is possible until the blister has healed. Blisters can become infected and should be seen to immediately. One drop of Lavender and/or Camomile on an open blister can stop it from becoming infected. Alternatively dilute 2 drops of Tagetes oil in 2 drops of iodine and apply to the area. If you are susceptible to blisters, an old dancers trick is to soak your feet in cold tea! Just make a pot of tea, add it to a bowl of water and soak your feet for thirty minutes.

People who are particularly liable to get blisters - joggers, hikers, athletes and ballet dancers, for example - use tincture of Benzoin (Friars Balsam) painted on the toes, or other vulnerable parts of the foot, both to prevent and to heal blisters.