According to the Mayo Clinic, the most common cause of a yellow tongue is an abundance of bacteria that produce a yellow pigment. This is often due to inflammation of the papillae on the tongue, which bacteria then latch onto, according to Ora Brush.
Ora Brush states that certain foods, such as spicy or acidic foods, as well as caffeine, alcohol and tobacco, can cause an adverse reaction on the tongue, causing the papillae to swell, which then attract unwanted bacteria that latch onto the papillae. This buildup of bacteria then leads to a yellow film, bad breath and the potential for bacterial infection. Ora Brush also describes a yellow tongue as the first stage of a harmless condition known as black hairy tongue.
The Mayo Clinic advises that a yellow tongue that persists for more than a few days is a potential indication of liver or gallbladder problems, particularly if it occurs along with yellowing of the skin and the whites of the eyes. In this case, the Mayo Clinic advises that it is important to seek medical attention as quickly as possible.
According to the National Health Service, or NHS, drinking lots of water and gently scraping the tongue with a tongue scraper can help resolve the issue. However, the NHS also advises people to seek medical attention if the problem persists, the tongue hurts or other symptoms develop.