solarmeter

I dare her to do a post 4 paragraphs long!

Don Smith

FYI:

How do YOU answer the question - Is a "tan" a sign of skin damage?

If you are not sure how to answer it, you had better be there tonight!

Don "Keeping YOU Informed" Smith

BooBop

Quote:
On 2002-06-01 10:47, solarmeter wrote:
I dare her to do a post 4 paragraphs long!

I pass on the dare Steve.

Mori

What we call a tan is a sign that PROTECTION from burn is present and as an offshoot, because of photo oxydization, clearly visible.

The start of the process that I visualize is that much like the drum in our ear receiving a signal... the signal can be low, yet audible enough to "hear" or loud enough to damage. Like the sound waves that strike the ear drum, melanocytes are "hit" by certain solar wavelengths and react by releasing a thick gooey, clear (the pink is from blood) liquid called melanin. The secretion is caused by the sensation of the presence of rays around the 318 nanometer range. These rays excite the melanocytes into discharging melanin (a direct product of absorbtion of Tyrosine by the melanocyte) in throughout the moisture of the "effected" skin. The melanine is itself the protective agent against further intrusion of light energy to the lower levels of the skin, much like creating a suit of armour. Melanin does not need to be dark in order to offer the protection but thankfully it is, otherwise we would all be in a different business. The UVA ray, in the presence of oxygen "photo oxidizes" the melanin and turns it brown.

Tanning therefore should be looked at as two seperate stages...

(1) the release of melanin into the moisture of the skin (caused best by UVB... If we use more intense wavelengths of UVB the activation process of melanin discharge will be heightened in quantity as well as speed, but the dangers of overexposure to the skin will also be amplified leading to a greater risk of burn. Also, even at the low, low intensity wavelengths of UVB, overexposure is also relative to time, even a small amount, but for too long a time will lead to overexposure)

(2) The Photo oxidization of the existing melanin. The clear melanin will change colour to a brownish tinge much like metal will turn brown when exposed to oxygen. The melanin however needs light (specifically UVA) in order to allow the oxygen to function properly, thus the term photo(light) oxidization (oxygen). This step of photo oxidization requires time (just as the process of causing the melanin to secrete needs time) and the UVA and oxygen continue to work after the causal effect (sunlight or sunbed) turn off, that's why we see ourselves getting darker AFTER exposure and even during darkness as evidenced by the greater darkness of our melanin when we wake up the next morning.

So we now have a formula: Melanin (as presented by exposure to low wavelength levels and quantities of UVB, ideally) + UVA in the presence of oxygen + Time = TAN.

And as a formula we can see that, if you increase any or all of the Melanin, UVA/Oxygen, and/or Time, the effect is a "greater" Darkness.

The above is NOT from a scientific report... it just makes the process so "easy" to understand and when taken to understand that the process occurs in the moisture of our skin, lotions become vital.

If I go to punch you on the nose and you block that punch we can describe the blocking as a protective mechanism for our nose. If you raise your hand to block the punch AFTER I punch you on the nose... no protective mechanism in play. So a protective mechanism by definition must come into play BEFORE damage can occur. So what exxactly does the presence of melanin protect us against???

Well, IMHO, I look at the tan like I look at callouses on my hand... I've hurt my hand the first time I chop a cord of wood. A callous, the size and thickness of which is determined by the damage (measured in the amount of wood chopped) will form in anticipation of further stress. Should I continue to chop 1 cord of wood daily or weekly the callos will stay the same. The callous is there to protect against damage occuring again. If I stop chopping wood for a long time, then go back to chopping that same 1 cord quantity, I will againd damage my skin and new callouses will for. Also, If I decided one day, after having chopped the same 1 cord quantity for some time, to chopp 2 cords, the 1 cord callous would not be sufficient protection against 2 cord and I will have damaged my skin again BUT a new, thicker callous will form, in anticipation of 2-cord damage.

hope this helps.

Teresa

Great explaination Mori. I still get pretty overwhelmed with all the specifics and you helped put in laymans terms.
So I just have one question. If I alternate between my upgrade beds (higher concentration of UVB and my stand up VHR (higher concentration of UVA) is that the best way to get optimum results????

Mori

Why are your higher UVB beds upgrades ?????

But you do have the right idea... first you cause the melanin to flow (UVB), next you cause the melanin to darken (UVA + Oxygen + Time).

Thanx for compliment. Understand though that I use this as a "simple" explanation of a not so simple biological process. A photobiolgist could rip me apart but we're NOT doctors... we just need to know how things work basically.