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Tattoos have often been presented
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in popular media as either marks
of the dangerous and deviant
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or trendy youth fads.
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But while tattoo styles come and go,
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and their meaning has differed
greatly across cultures,
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the practice is as old
as civilization itself.
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Decorative skin markings have
been discovered in human remains
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all over the world,
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with the oldest found on a Peruvian
mummy dating back to 6,000 BCE.
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But have you ever wondered
how tattooing really works?
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You may know that we shed our skin,
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losing about 30-40,000
skin cells per hour.
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That's about 1,000,000 per day.
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So, how come the tattoo doesn't
gradually flake off along with them?
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The simple answer
is that tattooing involves
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getting pigment deeper into the skin
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than the outermost layer that gets shed.
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Throughout history, different cultures
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have used various methods
to accomplish this.
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But the first modern tattooing machine
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was modeled after Thomas Edison's
engraving machine
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and ran on electricity.
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Tattooing machines used today
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insert tiny needles,
loaded with dye, into the skin
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at a frequency of 50
to 3,000 times per minute.
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The needles punch through the epidermis,
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allowing ink to seep deep into the dermis,
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which is composed of collagen fibers,
nerves, glands, blood vessels and more.
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Every time a needle
penetrates, it causes a wound
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that alerts the body to begin
the inflammatory process,
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calling immune system cells
to the wound site
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to begin repairing the skin.
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And it is this very process
that makes tattoos permanent.
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First, specialized cells
called macrophages
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eat the invading material in an attempt
to clean up the inflammatory mess.
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As these cells travel
through the lymphatic system,
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some of them are carried back with a belly
full of dye into the lymph nodes
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while others remain in the dermis.
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With no way to dispose of the pigment,
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the dyes inside them remain
visible through the skin.
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Some of the ink particles
are also suspended
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in the gel-like matrix of the dermis,
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while others are engulfed
by dermal cells called fibroblasts.
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Initially, ink is deposited
into the epidermis as well,
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but as the skin heals, the damaged
epidermal cells are shed
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and replaced by new, dye-free cells
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with the topmost layer peeling
off like a heeling sunburn.
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Blistering or crusting is not typically
seen with professional tattoos
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and complete epidermal
regeneration requires 2-4 weeks,
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during which excess
sun exposure and swimming
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should be avoided to prevent fading.
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Dermal cells, however,
remain in place until they die.
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When they do, they are taken up,
ink and all, by younger cells nearby,
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so the ink stays where it is.
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But with time, tattoos do fade naturally
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as the body reacts
to the alien pigment particles,
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slowly breaking them down
to be carried off
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by the immune system's macrophages.
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Ultraviolet radiation can also
contribute to this pigment breakdown,
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though it can be mitigated
by the use of sunblock.
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But since the dermal cells
are relatively stable,
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much of the ink will remain deep
in the skin for a person's whole life.
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But if tattoos are embedded in your skin
for life, is there any way to erase them?
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Technically, yes.
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Today, a laser is used
to penetrate the epidermis
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and blast apart underlying pigment
colors of various wavelengths,
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black being the easiest to target.
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The laser beam breaks the ink globules
into smaller particles
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that can then be cleared away
by the macrophages.
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But some color inks are harder
to remove than others,
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and there could be complications.
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For this reason, removing a tattoo
is still more difficult than getting one,
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but not impossible.
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So a single tattoo may
not truly last forever,
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but tattoos have been around longer
than any existing culture.
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And their continuing popularity means
that the art of tattooing is here to stay.
Krystian Aparta
The English transcript was updated on 2/13/2015.