Some influencers warn against sunglasses online.

Sleep thieves, vitamin blockers, cataracts: Some social media influencers consider sunglasses the devil's work. These laypeople's advice can be dangerous. What do the experts say?

Whether you're looking for a cool look or enjoying Breakfast at Tiffany's, sunglasses are more than just a matter of fashion. They protect against bright light and, in particular, ultraviolet (UV) rays. For medical professionals, any model with a UV 400 filter is an advantage. Such glasses block UV rays in the 280 to 400 nanometer wavelength range, which can be harmful to the eyes.

The more coverage a pair of glasses provides, both front and side, the better. Price isn't a factor. There are also affordable models with the right UV filter.

This takes the wind out of the sails of social media users who argue that sunglasses are purely a profiteering tactic. In general, it's advisable to protect your eyes when the UV index is above 3. Information on the current UV index is provided by the German Weather Service and various weather apps, for example.

The retina of the eye is the only part of the central nervous system that comes into direct contact with UV light, according to the Eye Foundation, which is dedicated to research, continuing education, and education in the field of ophthalmology. This particularly affects children and adolescents because the lens's function as a UV filter is not yet fully developed, explains Frank Holz, director of the University Eye Clinic Bonn and chairman of the foundation online.

But even in adults, UV rays can impair eye health, warns Gerd Geerling, director of the University Eye Clinic Düsseldorf and media spokesperson for the Eye Foundation. Malignant skin cancers of the conjunctiva are known. UV light is also known to promote the development of various types of eyelid cancer. Last but not least, high UV exposure accelerates the development of cataracts because the high-energy light damages the proteins in the lens. When social media claims that wearing sunglasses promotes cataracts, this is false.

Sunlight hits the eye level, especially in the morning and evening hours. They should therefore be worn for longer than just at midday. Extra caution is required at the seaside and in the mountains, where sunlight is even more intense because it is reflected by the surroundings. Advice from online users to deliberately squint into the blazing sun for better health is misleading. Sunglasses do not impair the body's vitamin D production. The skin around the eyes is far too small for that.

Sunglasses don't prevent sunlight from reaching the eyes anyway. Depending on the tint, they simply absorb a large portion of this light, explained Klaus Rohrschneider, an ophthalmologist at Heidelberg University Hospital, to the "Tagesschau" news program. Even with sunglasses, more light still reaches the eyes than on a cloudy winter day. The claim that sunglasses disrupt your circadian rhythm, as some authors claim on social media, is therefore also false.

From real doctors to Dr. Google, the topic of health is highly relevant, says communication scientist Nadja Enke of the University of Leipzig. However, social media influencers don't undergo any structured training, and there are no ethical, legal, or organizational regulations for them. Some take advantage of this. It's primarily about business.

For example, many influencers advertise their coaching services or alternative products. "They combine information and advertising space," says Enke. And what helps against harmful online tips? "Control bodies," says the expert. But every reader can also verify information themselves. Many medical associations operate their own online pages for laypeople. The Federal Institute for Public Health is also a reputable source.