MY father experienced a very painful rash on his back, concentrated on just one patch of his skin. The doctor told him this was shingles. What is shingles? I have heard the term before but I don't quite know what it is.

Shingles in a skin rash caused by the virus that also causes chickenpox.

It is also called herpes zoster. The virus is called varicella zoster, and it belongs to the herpes group.

If it is caused by the same virus that causes chickenpox, then why do some people get chickenpox and others get shingles?

Shingles usually occurs years after you get chickenpox. Once you have had chickenpox, you are immune to getting chickenpox again.

But the varicella virus may still remain in the body's nervous system - in particular, the nerves.

Under certain conditions, such as stress, immune deficiency (like with AIDS, or a cancer patient on chemotherapy drugs), the body's immune system is suppressed. The virus can then be reactivated and cause shingles.

And once you have suffered from shingles, you are more likely to get it again.

In fact, one out of every three people who has had one episode of shingles are going to get a recurrence.

In the US, up to a million people get shingles every year. Shingles commonly occur in people above age 60, however.

Since shingles is called herpes zoster, is it some sort of herpes? I don't like the word "herpes". It denotes a sexually transmitted disease.

Shingles may be called herpes zoster, but it is not synonymous with the disease, herpes, as you know it.

The virus that causes mouth sores and genital lesions is another type of herpes virus.

Shingles is contagious. If you have shingles, you can spread it easily to another person who has not had chickenpox. The strange thing is - these people catch chickenpox instead, and not shingles!

If I have shingles, when will I know if I am contagious. How long do I have to stay away from my loved ones?

You have to stay away from your loved ones for as long as you have new blisters forming and old blisters healing.

It's pretty much similar to the duration of quarantine for chickenpox.

Only when all your blisters crust and the virus can no longer be spread can you go out and mingle with people who have not yet had chickenpox.

What is the difference between chickenpox and shingles? How can I tell one from the other?

It's quite easy. The rash of chickenpox appears all over the body, but the rash of shingles appear only in one patch of the skin.

Before a rash even appears, you may feel a burning pain on a patch of your skin, and it may become very sensitive. This can go on for several days, up to a week. During this time, you are actually not sure what you are getting.

Then small blisters on a red patch begin to appear. New blisters come up. This happens for three to five days.

The patch of skin involved is the patch serviced by a particular nerve, the same nerve that hosts the varicella virus that has lain dormant all these years in your body.

Shingles is likely to affect the nerves of your body that service the patches/bands of skin on your trunk or back. These bands are called dermatomes. So the blisters will only appear on the dermatome.

Usually only one dermatome is involved.

Like chickenpox, the blisters itch, pop, ooze out liquid, and then crust over as healing begins. This whole process may last up to four weeks.

There is one variant of shingles where pain is present, but the blisters never appear.

Is shingles dangerous?

That depends on where the shingles is affecting you.

Usually there are no complications.

But sometimes when you scratch too much and bleed, your blisters can get infected with bacteria, then you can have cellulitis.

Or if shingles affect your face, particularly in the region of your forehead and nose (once again, a dermatome serviced by your fifth cranial nerve), your eye can be affected.

Is there any medicine for shingles? Do I just have to suffer quietly until it goes away?

There are definitely antiviral medication for shingles. Acyclovir and a similar family of drugs should be taken early, especially within three days of the first appearance of the rash.