Tattoos are a way to express creativity, individuality, even loyalty (though in the latter case designs often end up getting removed if loyalty fades). Sounds appealing but the idea of permanence leaves people hesitant. Enter the widely advertised, semi-permanent, 鈥渟tick-and-poke鈥� tattoos. Let鈥檚 poke the science.
The process is quite literally spelled out in the name. Except the stick is more of a needle. You can purchase packs of tattoo-grade needles online, or you can opt for a homemade gadget made by shoving a sewing needle into a pencil eraser, with some string wrapped around to hold the ink. Then, you poke your skin with it. The only major difference is that these tattoos are done by hand, not machine.
Our skin has three layers before hitting muscle -- the epidermis on the outside, then the dermis in between, and finally the subcutaneous tissue. For a tattoo to be permanent, the ink-drenched needle must reach cells in the dermis layer. However, cells in the epidermis undergo turnover as older cells are shed and are replaced by new ones. Any ink held in this layer will also be shed. Cells in the dermis are not shed, hence the injected ink stays in place.
The body recognizes ink as a foreign substance and responds by sending an army of macrophages, a type of white blood cell, to fight the intruder. Macrophages attempt to protect the dermal cells by engulfing the foreign material (phagocytosis) but when they die, they release the pigment, which quickly gets recaptured by a new generation of macrophages.
Truth be told, there鈥檚 no great difference between the two tattooing techniques: at the end of the day, you鈥檙e still pushing ink under your skin. The misconception of semi-permanence comes from the notion that the ink only tints cells in the epidermis -- the layer that sheds off. So, by the time all the cells in that area die and turn over (which can take up to a few months in adults), the tattoo fades.
Now for the flaw. Most people (especially if you鈥檙e doing a DIY stick-and-poke) have no idea where the epidermis ends, and the dermis begins. The epidermis is 1.5 mm thick in the most calloused parts of the body. So quite often, experimenters push too deep, and end up with a design that will last them a lifetime (or at least much longer than a few months).
Even though temporary stick-and-pokes sound appealing, the chance of successful application is small. The odds of the tattoo fading completely are slim. So, if you really yearn for a tattoo, instead of the stick-and-poke, stick to the pros. However, if you are not sure about living for the rest of your life with a design that seems appealing at the moment, go for a washable one that just stains the surface of the skin. Or give a try to henna, a dye extracted from the Lawsonia inermis plant that will fade away after a couple of weeks. Consider also that when it comes to 鈥渟tick and poke,鈥� your fine motor skills may not be as accurate as you think鈥� better bare than botched!
