"Beauty is only skin deep." This expression means that beauty is only a temporary surface quality. And some beauty products can cause lasting damage that goes far below the surface of the skin.
But people, especially women, will risk a lot for beauty.
In the United States, many people use sunlight and non-natural light to darken their skin.
Health experts advise against what is called "tanning" because of its links to skin cancer.
In the African country of Senegal, some women take health risks trying to do just the opposite. They use products that lighten the skin.
A model has her makeup done backstage at a fashion show in Dakar, Senegal for Dakar Fashion Week.
The World Health Organization says that 25 percent of Senegalese women use skin-lightening products on a usual basis. These products can contain chemicals such as mercury, hydroquinone and sodium hydroxide. These are dangerous ingredients that can cause cancer and possibly other physical damage to the skin. They can actually burn the eyes and skin.
An average beauty supply shop in Dakar has many kinds of skin-lightening creams and soaps.
Shop worker Adama Diagne advises her visitors to avoid the stronger products that promise fast results. She uses a cream that is made from carrots and not the strong chemical, hydroquinone.
She says that it is a personal choice and that no one pressures her. She says that some women want to be black every day. But for her, she likes to be a shade of brown.
Women in Senegal say they lighten their skin for the same reasons women all over the world make changes to their appearance. They say they want to look beautiful, to find a husband, or to stand out in a crowd.
But some products are so strong they must be mixed with others before they are used. One such soap is called "Day Before the Wedding."
This thinking troubles Senegalese filmmaker Khardiata Pouye Sall. So, she made "This Color That Bothers Me," a film about the subject of skin lightening.
Young Senegalese woman loving the skin she's in.
"I used the most shocking images so that women would see the dangers. It is hard to understand why a woman would tell herself that dark skin is not beautiful. It is in their heads. They want to please a man, to be loved. Or they want to please society, to succeed."
Ms. Sall says the government needs to better control the marketing and sale of skin lighteners. But she adds education is the best way to persuade people against using them.