The process of getting a tattoo involves pushing ink down into your ‘second layer’ of skin, or the dermis.
In the same way that your body tries to force out splinters, it will recognise this ink as a foreign object and try to remove it.
The way it does this is to send white blood cells to destroy the ink particles. The only problem is that the ink particles are larger than the white blood cells, making this process extremely slow.
Slam d-inking! A man has a tattoo of a basketball player applied to his leg during the Great British Tattoo Show this weekend
This is why tattoos start to fade naturally after a few decades.
Also, having a tattoo alters the way people sweat, research revealed last April.
Tattooed skin produces less sweat, while the perspiration it does secrete is higher in sodium, a study by Alma College in Michigan found.
Tattooing involves permanently placing ink around 3-5mm under the skin, which is the same depth as sweat glands.
Whether a person’s long-term health is affected by reduced sweating is unclear, however, perspiration is critical to regulating body temperature, with overheating eventually causing heatstroke.