My annual visit to the dermatologist was last week. Everything went well. No suspicious moles or skin abnormalities were found. Just as we should have periodic medical checkups and dental visits, we must be vigilant in keeping our skin healthy.

The dermatologist practice I frequent also has a spa for non-medical, aesthetic services, and includes a special lounge reserved just for guys. I opted for some laser work to remove those annoying little red spots (hemangiomas) that crop up in us older guys, so I got to hang out in the lounge. High-def TV, nice recliners, coffee and booze (the good stuff, like Hendrix gin and Basil Hayden's whiskey) were freely offered. This kind of pampering makes doctor visits much more pleasant!

A young man lounging in a bathrobe was already present when I arrived and struck up a conversation. Since he didn't appear to need botox or moles removed I -- being the nosy, inquisitive type -- asked what procedure he was having. He replied that he was having some tattoos removed. I didn't ask to see the tattoo or even inquire as to its nature because we are guys and aren't supposed to care that much about such things. I just went back to sipping the free Basil.

Because I'm a scientist, I started thinking about the science behind tattoos. I never had one, never wanted one. I don't judge those that do, either. I do know what is involved in getting a tattoo. Ink is injected with a fine needle just under the skin with a minimum of discomfort usually. Have you ever wondered why a tattoo is permanent? Our skin cells have a limited life span of two to three weeks. Why doesn't the ink come out with the skin cells?

The reason is that the ink isn't actually in the skin cell. When the ink is injected into the dermis, the middle of three layers of skin cells, it causes an immediate immune response and macrophages come rushing to the site of injection. Macrophages are white blood cells akin to trash trucks: they pick up things that are foreign to our body and engulf it, sort of like a Pac-Man. Unlike Pac-Man the macrophages settle into the dermis after "eating" the ink and stay there until they die. Macrophages can live for years. When the ink-laden macrophages die the ink is released into the dermis. New macrophages in the neighborhood then recycle the ink by engulfing the pigments. This recycling process occurs repeatedly and never lets the ink get taken away from the injection site. This is why it is so difficult to remove a tat.

Now, dermatologists offer specific laser treatments that burst the macrophages and fragment the ink particles into smaller pieces. This then allows the ink fragment to be carried into the body's lymphatic system and disposed of properly. Several laser sessions are usually needed to completely remove the pigments due to those pesky macrophages continually gulping them down and planting themselves in the skin.

As I said earlier, I don't judge those who want to decorate their skin with a girlfriend's photo, snakes, roses or the Constitution. Just remember what your body goes through to handle your need for bodily advertising.

-- Devin Houston is the president/CEO of Houston Enzymes. Send comments or questions to [email protected]. The opinions expressed are those of the author.