Tattoos are made by injecting pigments into the skin

Tattoo inks are largely unregulated by the FDA

With hundreds of ink manufacturers, all unregulated by the FDA, it’s hard to determine the exact ingredients in tattoo inks. Some pigments may contain carcinogenic chemicals, such as heavy metals and aromatic hydrocarbons, or even bacterial contaminants. Red ink often causes allergic reactions and may even contain lead or mercury.

The immune system fights tattoos

Our skin is a fascinating organ that wants nothing more than to protect our bodies from the outside world. Tattoos penetrate that protective wall to inject ink directly into the sensitive, immunologically rich layer of skin known as the dermis.

Tattoos, explained

Tattoos last because immune cells trap ink beneath the skin—but there's more to the story. This overview looks at how ancient cultures used tattoos for status, spirituality and punishment; how technology like the electric tattoo machine transformed the art form, and where innovations like smart tattoos could take it next.

Tattoo removal breaks apart ink particles

Tattoos place ink below the skin's surface layers in packets too large for white blood cells to clear out. By breaking the ink into smaller pieces, the immune system, which is responsible for removing foreign matter, can process them.

Tattoos remain visible on your skin thanks to immune cells called macrophages

Technological breakthroughs are spurring innovations in the industry

What if you could see your tattoos before they’re embedded in your skin? Or take a virtual visit into a local studio to work out your nerves over a first tattoo? The industry is anticipating some big technological changes, from 3D designs to sci-fi upgrades to more precise tattoo guns.

Harvard and MIT researchers are developing life-saving tattoos

Tattoos aren’t just a fashion statement. Scientists are trying to find life-saving applications for them. Harvard and MIT researchers are developing tattoo inks that react to body chemicals, alerting diabetics to blood sugar fluctuations or athletes to dehydration. Someday, patients may observe their body chemistry with tattoos that change colors.

Samuel O’Reilly patented the tattoo gun in 1891

Before the tattoo gun's invention, recipients sweated while artists slowly tapped or sliced designs into their flesh. The tattoo gun changed the field, helping artists ink clients’ skin at incredible speeds. Inventor Samuel O’Reilly applied the basic idea of an electric pen invented by Thomas Edison to his tattoo gun.

'Skin stitching' is an ancient tattoo method that's made a comeback

In the slow method, artists use needles to puncture the skin. Then, pigmented thread is drawn through the punctures to create the tattoo, resembling embroidery in the flesh. The method is experiencing a cultural revival within Canada’s First Nations communities.

'Magic ink' is redefining the tattoo

One University of Colorado professor has developed an ink that can be "turned on" with exposure to UV light, and "turned off" with sunlight. While the ink could help those who want to hide their body art from family members or coworkers, there are potential uses for medical procedures.

There are stigmas attached to tattoos

Although tattoos are fairly common in the US, some taboos remain. A 2017 study in the Journal of Social Psychology found discrimination against tattoos is alive and well, and that even individuals with tattoos associate them with negative stereotypes.

'Tattoo' comes from a Polynesian word that means 'to strike'

“Tatatau” roughly translates to “strike,” a reference to the ancient process, which involved tapping ink into the skin with sharpened objects, like the bronze implements used circa 1450 BCE in Egypt, below.

Knowing how to use an EpiPen is a life-saving skill—learn how with this video

If someone has a severe allergic response, including trouble breathing or two or more allergic symptoms, it may be necessary to administer epinephrine, usually through an injection. Epinephrine autoinjectors—often called EpiPens—should be injected into the mid-outer thigh, even through clothing, for about 10 seconds, depending on brand. Sometimes another injection with a separate EpiPen is required if the patient does not get better after a few minutes.

Pig-to-human transplants have raised concerns about pig living conditions

Pigs are the current first choice for xenotransplantation procedures, yet such work gives some researchers and animal welfare advocates pause. Concerns include that pigs would have a poor quality of life since the animals must live in a strictly-controlled, hyper-clean environment to avoid risky pathogens.

On average, people smell worse if they're sick

For a small 2014 research study, a panel was tasked with sniffing the smelly t-shirts of people who had been injected with a compound known to activate the immune system and those of controls without the shot. It found that those who were acting as if unwell (due to the injection) generally smelled worse. Subsequent work found that those who sniffed unpleasant odors had a mild immune response of their own—perhaps to protect them from disease. (Some users may experience a paywall.)

Fiber lasers used for metal engravings can’t burn your skin

These devices use diodes and mirrors to create pulses of light that vaporize metal in billionths of a second, though at wavelengths that cannot react with organic material. Pulse width, power, and speed adjustments can produce white, black, and even colored patterns through controlled heat reactions.

Needle-free polio vaccines were offered in Afghanistan for the first time in 2026

Fear of needles has been one barrier to eradicating polio in Afghanistan. Vaccinators are now using a needle-free jet injector to deliver the vaccine through the skin—an approach that's previously been used in other locations. The inoculation includes the inactivated virus vaccine (the vaccine without any live virus in it).

Allergy tests identify antibodies, but not whether allergy symptoms may appear

Skin prick tests and blood tests, the two most common allergy tests, both detect the presence of allergen-specific antibodies. But just because the body has those antibodies doesn’t mean that a person is “allergic” to a substance or that they will develop symptoms of an allergy when encountering the substance. Allergists work with families to interpret the results and sometimes combine that data with approaches including exposure challenges—giving someone a tiny bit of the food or substance they may be allergic to—under medical supervision.

Watch the safe way to remove a tick from your body

Minimizing your risk of Lyme and other tickborne diseases hinges on quickly removing ticks. To do so, place tweezers on the animal as close to the skin as possible and then pull directly upwards to try to avoid leaving bits of the tick's body behind. If possible, try to take a photo of the tick to share with your doctor to better identify potential disease risks (since certain tick species can carry specific diseases). Next, dispose of the tick without crushing it in your fingers—flushing it down the toilet, or placing it in alcohol or a sealed bag—and then thoroughly wash the bite area and your hands.

See this diverse list of vector-borne diseases

Human illnesses caused by parasites, viruses, and bacteria, and transmitted by a living organism—often small, bloodsucking ones like mosquitoes, ticks, and sandflies—are known as vector-borne diseases. That carrier is called a vector. These diseases disproportionately affect the poorest populations in tropical and subtropical areas.

Mosquito necroprinting uses an insect's mouthpart as the printer nozzle

Mosquitoes are abundant, and their nozzles are 32-100 times cheaper to harvest than to create from scratch out of metal or glass. By coating the organic nozzle to increase its strength, researchers are employing necroprinting to create tiny structures at better resolutions than commercial alternatives.

See why wearing earbuds—instead of over-the-ear headphones—can cause ear infections

Earbud headphones can heighten the risk of ear infections. They can lead to earwax buildup and create a dark, moist environment as you sweat—ideal conditions for germs to thrive. Wearing external over-the-ear headphones or ones that don't enter deep into the ear canal can help.

Learn how to make a print like Andy Warhol

Warhol's signature printing style was a practiced balance of mass-production silk-screen techniques and deliberately introduced hand-painting and imperfections.

Understanding vaccine side effects

A vaccine is a medical intervention, and as with any medical intervention, may have side effects. This article discusses side effects and adverse events related to vaccination.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

See images of medical cases of firework injuries shared on this 'Instagram for doctors'

Included photos include scans of missing or damaged digits, a chunk of missing flesh, a facial injury from a homemade firework in a glass bottle that exploded in the patient's hand before it was thrown, and an injury where a patient's finger bone flew into someone's leg.

Learn about ionizing radiation and see the most radioactive places on Earth

The average person is exposed to radiation every day, though most of it is either harmless non-ionizing radiation or ionizing radiation at doses too small to significantly affect an individual. The highest doses of ionizing radiation are received by smokers due to the radioactive polonium and radioactive lead in tobacco products.

Firework or sparkler burns, even if they cover a relatively small area of skin, can significantly affect our range of motion.

Poison ivy is in the same family as mangoes, cashews, and pistachios—and they all produce oily urushiol in their raw, unprocessed state—but they are typically prepared in ways to avoid causing human discomfort.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

See these 16 pieces of art evoking phobias of snakes, flying, spiders, and more. 

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

Watch the cumbersome, but necessary, precautions healthcare workers must take to care for and protect themselves while caring for Ebola patients.

Art theft is the third-largest source of criminal revenues worldwide, thanks in part to the subjective nature of valuing a work of art.

About 2,000 US babies are born annually without some portion of their limbs, potentially leading to a lifetime of pricey prosthetics.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

Objects can be 3D printed with light by projecting 2D computerized tomography (CT) scans onto rotating cylinders of resin, which solidify upon exposure.

Telehealth demand for GLP-1s for weight loss is booming as consumers seek easier access.

This site reaches millions of visitors who are tired of AI chatbots and seeking human connection. Pretend to be an AI chatbot and ask questions, provide answers, and draw for people in real time.

Abraham Lincoln was almost assassinated weeks before his inauguration as he traveled from Illinois to DC through Baltimore in 1861; it took two independent claims for Lincoln to be convinced the threat was real

The original copy of the Declaration of Independence is not a pristine document, and even features a smudged anonymous handprint in the bottom left corner.

An initial public offering or 'IPO' is the process of a private company becoming public by putting shares of the company on the stock market for purchase.

Some coin denominations have ridges etched on their sides, partly to prevent counterfeiting, in a practice called 'reeding.'

The US first hosted the World Cup in 1994, a tournament that lives in soccer infamy for its poor planning and the murder of Colombian player Andres Escobar, who'd accidentally scored on his own net.

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

Dorothy's famous entrance into Oz in 'The Wizard of Oz' relied on analog tricks, including a body double and sepia-toned paint, as much as it did on technology

In 2018, 26-year-old missionary John Allen Chau was killed by tribesmen after attempting to reach and evangelize on India's isolated North Sentinel Island

One of the most famous portraits ever taken is 'Afghan Girl' (1984) by Steve McCurry, yet the subject Sharbat Gula went much of her life without being identified or benefitting from the image's success.

Prince's sexually explicit 1984 track 'Darling Nikki' attracted the ire of the Parents Music Resource Center, an advocacy group that inspired the Parental Advisory sticker, even though the song ends with a Christian message.

Power lines are dotted with large, brightly colored balls to improve the visibility of these thin wires to helicopters and small planes and help prevent potential crashes.