BehindTheMedspeak: Why do bags form below our eyes?

It's a question I've had since forever, so I figure there may be others who've also wondered.

Below, Dr. Rhoda S. Nairns, clinical professor of dermatology at New York University School of Medicine and president of the American Society for Dermatologic Surgery, gives the most complete, understandable and logical answer I've ever come across.

It appeared in the February 2005 issue of Scientific American, in their "Ask the Experts" feature.

Dr. Nairns omitted two things that perhaps she takes for granted you'd be aware of.

I, on the other hand, know that one should take nothing for granted insofar as it involves joeheads.

Let me note the two most important things you can do to mitigate the severity of dark circles and bags under your eyes:

1) Avoid sunlight to the face. It destroys skin, rendering it prematurely old and inelastic.

2) Avoid cigarettes. The constituents of cigarette smoke age blood vessels prematurely, destroying the microcirculation. When subcutaneous tissues don't get blood, they also stop receiving oxygen and die. Dead connective tissue sags.

Without further ado, here's what the dermatologist had to say.

Dark circles and bags under the eye occur for several reasons: the skin there is much thinner than it is elsewhere on the body and becomes looser as we age.

This very thin skin also sits on top of underlying purple muscle and blood vessels and therefore appears darker.

In addition, some people have hereditary pigmentation in this area.

As we age, fat comes out of the space enclosed by the eye socket, called the orbit, and forms a puffy area under the eye.

This fatty tissue can fill with water, making the hollow appear even deeper.

The condition becomes even more noticeable when water is retained in the fat pad, which can occur for a variety of reasons, including eating too much salt, lying flat in bed, not getting enough sleep, allergies and monthly hormonal changes.

Treating the hollow space under the eye is straightforward and can be done by injecting a filler such as Restylane.

Immediately after this procedure, the so-called tear trough is softened, and any visible pigmentation becomes noticeably lightened.

A carbon dioxide (CO2) laser also can be used to resurface the skin, which tightens and thickens it as well as lightening the coloring.

For hereditary pigmentation, CO2 laser resurfacing and bleaching creams are sometimes helpful.

As an option, a surgeon can perform blepharoplasty to fix the fat pad under the eye.

Simple, nonsurgical measures to reduce the puffiness and darkness of under-eye circles include avoiding salt, using cold compresses on the eyes, getting enough sleep, treating allergies, as well as sleeping with your noggin higher by resting it on two pillows or raising the head of the bed.