While light therapy definitely played a role, it wasn't the only thing that sparked the fascination with a darker skin. It was only in the 1920s that tanning was made trendy by the fashion pioneer Coco Chanel
Rumour has it that photographs of her surfaced after she had sunbathed too much on a cruise. Chanel, who was known for her pioneering work in the fashion industry, immediately started a trend: Women unleashed the shackles of the Victorian era and took on a new minimalist style – combined with a “healthy glow”.
When colour movies and television became prevalent, actresses wanted a tanned skin to look better on the big screen.
As tanning became popular, so did sunburn, however, which opened up the market for products such as tanning oils.
By the 1960s, tanning was just as much as status symbol as pale skin used to be. A tanned skin suggested summer holidays on tropical islands, an outdoor lifestyle, fitness and overall robust health.
And if you couldn’t afford a life of leisure, what did you do? Tan in your back yard, or get a fake-tan, of course. Tanning beds and indoor tanning took off all over the world.
People already made use of sunlamps in the 1930s, while the first commercial tanning beds made their appearance in the USA by 1978. The first self-tanner, Man-Tan, made its appearance in 1958, and by the 1990s, tanning beds and self-tanning products were widely available.
Sirius Times; Dr. Timothy Moore "The Science of Melanin," https://www.youtube.com/watch?v=yozORb1TE_I