Did you know? Tattoos are permanent thanks to immunology!
The immune system is involved in nearly every bodily process
Monday April 29th was International Day of Immunology, so I want to share a less widely known fun fact about the immune system!
For me, as someone who has been fascinated [obsessed?] with the immune system since my childhood days, the coolest thing about immunology is that the immune system is involved in pretty much every process in our body.
Many are obvious: developing oral tolerance to food antigens we ingest), patrolling our bodies and mounting a defense against invading pathogens, surveilling our own cells to limit the potential development of cancer, the progression of allergies, asthma, and autoimmunity, and more.
But the immune system is even involved in processes like pregnancy and fetal development (mild immunosuppression ensures people don’t reject the fetus during pregnancy), obesity, cardiovascular diseases, metabolism… you name it.
And yes: the immune system is the reason tattoos are permanent!
Tattoos are common in both modern and historical societies, and are a large part of many cultures and as a way of self expression. I myself have 6 tattoos - each with very specific and unique meaning, including 2 that are in honor of my late brother Brian, whom we lost to suicide in 2015.
The popularity of tattoos are increasing, much of that impacted by societal acceptance and reduced workplace stigma. Indeed, based on 2023 Pew Research data, 32% of the American adults have a tattoo, a rate that is up from 21% in 2012.
Let’s all give a thank you to the dermal macrophages.
Tattoos utilize the dermal layer of skin, which is directly below the epidermis. The epidermis is your outermost layer of skin and sheds cells at a high rate, as a result of being your first line of mechanical defense.
Within the dermis, you have specialized innate immune cells called dermal macrophages (big eaters). Macrophages are cells of the innate immune system that engulf pathogens or foreign invaders and destroy them. Macrophages differentiate from monocytes which circulate in our bloodstream, but once they end up in the skin, they stay their for their lifespan. They don’t even leave the skin to migrate to the lymph nodes, unlike other types of immune cells! Within the skin, you’ll find them in the dermis and around the hair follicles, a reflection of the roles they play.
So, as you might guess, dermal macrophages are pretty important to our largest and fastest growing organ - the skin. Dermal macrophages maintain skin homeostasis, salt balance, and even hair growth. They participate in nearly all wound healing processes within our skin: inflammation, tissue formation, and maturation.
In order to do that, these macrophages are constantly surveilling the skin for insults: physical wounds (cuts and scrapes), invading pathogens that may enter the skin through a wound or an insect bite, and more.
Dermal macrophages respond to the physical process of tattooing.
There are multiple ways to get tattoo ink into the skin, but it typically is always going to involve introducing ink (a foreign substance) into the dermis using a sharp object (that creates a wound).
In our culture, the most common and modern way is using a tattoo machine. Tattoo machines have one or multiple needles that move up and down extremely rapidly at a rate of 50-3,000 times per minute to break through the skin and insert ink into the dermis.
This process of puncturing the skin and introducing the foreign ink pigment particles triggers the activation of the immune system and the creation of an inflammatory response.
When ink is introduced into the dermis, macrophages engulf those particles using a process called phagocytosis and attempt to break it down. However, macrophage enzymes are unable to break down the ink and digest it within their specialized digestive compartment called the phagolysosome.
As a result, most of the macrophages that engulf ink simply retain the pigments and hang out in the skin, within the dermis. By retaining these ink particles, you can physically SEE the ink in the pattern it was tattooed, thereby making that tattoo permanent! Connective tissue cells called fibroblasts can also take up some of the pigment molecules and contribute to the longevity of tattoos.
While epidermal cells turn over faster, eventually dermal cells die as well (nothing lives forever, right?) When dermal macrophages die, they release the ink pigments and new macrophages engulf them. The new macrophages still cannot break down the pigments, so they contribute to the persistence of tattoos. On the surface, tattoos seem to be unchanging designs that last forever, but in reality they are the result of continuous and dynamic processes involving the immune system.
Pretty cool, right?!
Tattoo inks are not regulated before they appear on the market
In the United States tattoo inks and pigments are classified as cosmetics by the FDA but are not FDA-approved or regulated for safety. This means tattoo inks do not need pre-market regulation or approval, so ink manufacturers don’t need to submit safety data or prove their inks are safe before selling them.
It’s also important to note that there are over fifty types of pigments used in tattoo ink, and no color additives have been approved for injecting into the skin.
If certain batches of ink cause problems, they are recalled and dealt with, but these measures only occur after people report adverse effects. For example, if the FDA determines that a particular tattoo ink is causing adverse reactions or poses a health risk, it can issue warnings, seize products, or take legal action against the manufacturer. Investigations occur after there are outbreaks or adverse effects. As more data are gathered about tattoos and how they affect the body, the FDA will likely re-evaluate the regulation policies surrounding color additives.
Individual states may have their own laws and regulations regarding tattoo inks. Some states require tattoo ink manufacturers to register their products or comply with specific labeling requirements. There may also be regulations on tattooing practices and health and safety standards. But you should know that these types of regulations are not remotely as stringent as other substances we might get injected (say, vaccines?)
Separate from the lack of regulation of tattoo inks, there are other risks associated with tattooing. Of course, there are potential risks of infection as a result of a procedure that breaks the skin and injects a foreign substance into your body (especially one that is NOT regulated for safety)
Inks can cause allergic reactions or other skin issues at the site of the tattoo. For example, inflamed areas called granulomas can result from the tattoo process. More significantly, there is a risk of transmitting bloodborne diseases like hepatitis if the equipment isn’t properly taken care of or is shared between clients. The best way to avoid these issues is to make sure you go to a reputable tattoo artist who follows all safety procedures.
What about tattoo removal?
Tattoo removal is possible, but it is often a long and complicated process because we have to counteract the process that makes tattoos permanent.
The most common method of tattoo removal uses a laser. Macrophages cannot break down the ink pigments, so the laser destroys the cells and breaks apart the pigments into smaller aggregates so they can be cleared by the lymphatic and immune system. However, multiple treatments are often required because neighboring cells can take in the broken ink pigments before they are fully eliminate. Because of this, some tattoos cannot be fully removed. (Board-certified dermatologists can assist with the tattoo removal process)
Cognitive dissonance: tattoos versus vaccines.
Cognitive dissonance happens when an individual has conflicting attitudes, beliefs, or behaviors. This causes individuals to engage in compensatory behaviors to justify their actions. Cognitive dissonance leads to hypocrisy, where people avoid certain behaviors while simultaneously engaging in related activities. In many instances, these people will exhibit confirmation bias, only seeking information that supports their preconceived beliefs, and will often avoid the topic that they are trying to rationalize.
People who are opposed to vaccines but have tattoos are a perfect example of cognitive dissonance.
While both elicit robust immune responses after injection into the skin, vaccines are highly regulated for safety and efficacy and the ingredients are rapidly cleared from the body. In contrast, tattoos persist INDEFINITELY and the inks are not regulated for safety or injection into the skin.
Maybe if you encounter someone that this applies to, you might want to try a thought experiment with them…?
Of course, choosing to get a tattoo is totally your call. And I say that as someone with [unregulated] tattoos but also that gets every vaccine that is recommended for my demographic. Tattoos are a calculated risk I opt to take, whereas vaccines have decades and decades of data to demonstrate their immense benefit on both a personal and collective level.
I hope that this was a fun and interesting topic, and maybe you have a newfound appreciation for the immune system after reading this!
Thanks for joining in the fight for science!
Thank you for supporting evidence-based science communication. With outbreaks of preventable diseases, refusal of evidence-based medical interventions, propagation of pseudoscience by prominent public “personalities”, it’s needed now more than ever.
Your local immunologist,
Andrea