Richard E. Clopton septate at
Sun Mar 20 13:54:46 EST 1994

Niccy Scholfield (Scholfield at wrote:
: We were wondering just exactly how tattoos work. Unlike a protein dye that 
: comes off when the skin sloughs off, a tattoo is guaranteed for 99 years! 

: Niccy and Linda.

I don't profess to know all the answers, but I might be able to help you along
your way.  If any netter finds a glaring error--feel free to correct.  I'm
just an "old classical zoologist".  

Tattoos:  This is my understanding of how tattoos work-->
	The dyes/pigments are engulfed by macrophages.  Normally (or so I 
	understand) macrophages are wandering bodies; however, when they
	engulf enough material, they remain static until the material is
	digested or broken down.  The trick seems to be that they can't break
	down the pigments/dyes used in the tattoo process--thus they hang 
	around in the same place indefinitely.  Of course macrophages seem
	to be VERY long-lived cells--so they tend to remain "painted in 
	place" for a VERY long time.

	I suppose my question is--> why do tattoos fade over time?  Do the
	pigments break down over time, or do the colored pigments kill
	their macrophages faster than the balck/green dyes?  Don't know.

	Oops.  One other comment--> since macrophages are recognized as self,
	nothing else is going to come along and get rid of them -- adds
	to the permanency of the tattoo.

	Never had a tattoo myself, but I did accidently jab the back of my
	hand with a lead (madagascan clay & graphite ;>) pencil when I was
	about 7 or 8 years old.  21 years later the black dot is still right
	where I left the pencil lead--stuck inthe skin on the back of my hand.

Good luck, and I hope you get what you want,


R. E. Clopton		Center for Urban and Public Health Entomology
septate at 	Department of Entomology
Gregarines			Texas A&M University (Gig'em Aggies!)
"I don't mind a parasite, but I object to a cut-rate one." - Mr. Rick

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