While temporary body art may involve less commitment than permanent ink, it is certainly not harmless and may cause long-lasting allergies, US Food and Drug Administration (FDA) has warned.
Temporary "Black henna" tattoos typically last from three days to several weeks, depending on the product used for colouring and the condition of the skin.
Unlike permanent tattoos, which are injected into the skin, temporary tattoos marketed as "henna" are applied to the skin's surface, the FDA said.
However, "just because a tattoo is temporary it doesn't mean that it is risk free," said Linda Katz, director of FDA's Office of Cosmetics and Colors in a statement.
Some consumers report reactions that may be severe and long outlast the temporary tattoos themselves.
MedWatch, FDA's safety information and adverse event reporting programme, has received reports of serious and long-lasting reactions that consumers had not bargained for after getting temporary tattoos.
Reported problems include redness, blisters, raised red weeping lesions, loss of pigmentation, increased sensitivity to sunlight, and even permanent scarring.
Some reactions have led people to seek medical care, including visits to hospital emergency rooms. Reactions may occur immediately after a person gets a temporary tattoo, or even up to two or three weeks later.
Henna, a reddish-brown colouring made from a flowering plant grows in tropical and subtropical regions of Africa and Asia.
Since the Bronze Age, people have used dried henna, ground into a paste, to dye skin, hair, fingernails, leather, silk and wool.
This decoration - also known as mehndi is still used today around the world to decorate the skin in cultural festivals and celebrations.
However, today so-called "black henna" is often used in place of traditional henna. Inks marketed as black henna may be a mix of henna with other ingredients, or may really be hair dye alone, FDA said in a statement.
The reason for adding other ingredients is to create a tattoo that is darker and longer lasting, but use of black henna is potentially harmful.
That's because the extra ingredient used to blacken henna is often a coal-tar hair dye containing p-phenylenediamine (PPD), an ingredient that can cause dangerous skin reactions in some people.