A blister is a small fluid-filled pocket or swelling in the top layers of skin. A blister generally forms where there is damage to outer layer of skin. The fluid protects the underlying tissue against further damage by cushioning them and allowing healing.
The fluid in most blisters is clear fluid known as serum, that is blood without red blood cells and clotting factors. Sometimes, a blister may contain blood (blood blister) or pus when it is infected. Blisters may be single or multiple depending on the cause.
Blisters are generally caused when there is injury to skin due to friction, heat or reaction to a chemical or insect bite. Sometimes, they can be due to a medical condition.
Friction can cause a tear between the upper (epidermis) and lower (dermis) layers of skin. The intact surface of skin is then pushed out as fluid (serum) collects in this newly created space within the skin. Friction blisters are common in those in military or those who play sports regularly as their skin is subject to friction on account of their activity, especially if their shoes are ill-fitting or stiff. Blisters are more likely to occur on moist skin, such as sweaty feet due to non-absorbing socks.
Extreme heat or cold can cause blisters through a similar mechanism as in friction blisters. Exposure of skin to extreme heat occurs in burns, scalds, hot sun (sunburn), and chemical or electrical injuries. Exposure to extreme cold can also cause blisters as in frostbite.
Reaction to Chemicals or Insect Bites
Blisters can form on skin when it comes into contact with chemicals like cosmetics, solvents or detergents. They can also be the result of insect bites or stings that set up an allergic reaction.
Crushing or Pinching of Skin
If the skin is pinched, crushed or excessively squeezed, then tiny blood vessels that are closer to the surface of skin can rupture. This causes the blood to leak into the tear in between layers of skin.
Source : http://www.thirdage.com/hc/c/what-is-chickenpox
There are a variety of diseases in which blisters occur. In most of these cases they tend to be multiple and anywhere on the body, and not just on extremities. Examples of such diseases are chickenpox (viral infection, usually affecting children), herpes (sexually transmitted disease) and impetigo (bacterial infection of skin). Rarer causes include skin disorders like bullous pemphigoid, pemphigus and dermatitis herpetiformis.
Friction blisters tend to be common on extremities, such as on hands and feet, which are more subject to friction. Blisters due to other causes can occur in other places also.
Not all blisters are painful. Blood blisters and infected blisters tend to be painful. Some are tender on application of gentle pressure. Blood blisters are darker in colour, and an infected blister can be reddish or red streaks may be found leading away on the surface of the blister. The skin overlying an infected blister may also be hot to touch. In the case of blisters due to underlying disease, there may be other accompanying symptoms like fever, cold or cough, body aches and a general feeling of being sick.
Most blisters resolve within 3-7 days as new skin is formed underneath the blister, with the fluid getting gradually reabsorbed. Those that don’t may be infected or due to some underlying disease, in which case a doctor has to be consulted. However, do not break a blister because doing so with an unsterile needle or pointed object, which is more likely to be the case, can set up infection.
Most of the blisters tend to resolve on their own without the need for medical attention. As stated above, new skin will grow back, and the overlying skin dries up and peels off.
As noted above, you should not pierce the blister in an attempt to break it up. Allow the skin to remain intact so that infection can be avoided. Small blisters can be covered with an adhesive dressing (plaster).
You can use a gauze pad/dressing for larger blisters, taped to keep it in place. For painful blisters or ones that show signs of bursting, use soft dressing as a cushion. Dressing should be changed daily, making sure that you do so with clean hands.
If the blister bursts, do not peel off the skin overlying the blister. After the fluid has drained away, use a sterile dressing over the blister and surrounding area until it heals, so that infection is prevented. Hydrocolloid dressings are useful for this purpose.
After the blister has healed, you may want to change to better-fitting shoes, moisture-absorbing shocks or special socks designed for sportsmen. Always wear gloves when handling equipment or tools with your hands.
Blood blisters also can be allowed to heal on their own. Initial pain can be alleviated by applying ice pack for 10-30 min. A towel can be used to prevent direct contact between the blister and ice. If the blister bursts, then follow the regimen advised above.
These kinds of blisters need the attention of a medical doctor. Consult one as soon as possible. Antibiotics may be prescribed after puncturing and draining of the pus in the blister under sterile conditions.
Blisters due to Heat
These, too, tend to resolve on their own. Second-degree burns will need the attention of a medical expert. Hot objects should be handled with care. Moisturiser and calamine lotion can provide relief in the case of sunburns. Wearing sunscreen lotion can protect against sunburns when you are likely to spend a good deal of time outdoors. You could also try wearing a hat when you are outdoors.
Blisters due to Skin Reaction
The offending chemical needs to be identified and avoided in future. Protective gloves should be worn when handling chemicals in the future. Antihistamines can be taken for insect bites or stings. It may be advisable to consult a doctor for more specific management.
Blisters Due to Medical Conditions
Blisters in these cases definitely need the attention of a medical doctor. This is so not only to attend to the blisters but also to treat the other symptoms of the underlying disease.