This is a classic question, UVC deep ultraviolet has little harm to human skin, but it can cause significant eye damage. The typical UVC-LED wavelength of 275 nm ultraviolet light is almost 97% or more absorbed by the human skin's stratum corneum, 99.9% or more absorbed by the stratum corneum and epidermis, and a very small portion of the light reaches the dermis layer. Ultraviolet radiation can only cause skin cell carcinogenesis when it acts on the dermis layer. So it is generally believed that UVC ultraviolet rays have little effect on human skin. Of course, baby skin, including some human skin with a thinner stratum corneum, has poorer resistance to UVC ultraviolet rays. The human eye lacks protection from the stratum corneum. Direct UVC radiation can cause lens and corneal lesions. Therefore, it is forbidden for the human eye to directly look at the illuminated UVC-LED beads
The shorter the wavelength of light, the poorer its penetration ability, which is determined by the wave particle duality of light. Of course, when it comes to substances, it is also related to absorption. Is UVC deep ultraviolet radiation harmful to the human body? The most convenient answer is, yes, do not expose yourself to UVC ultraviolet rays. But in fact, there is a big misconception that UVA, such as 365, 385, and 395, can cause significant damage to human skin because this wavelength of ultraviolet radiation can penetrate the dermis layer of the human body and trigger skin cell carcinogenesis
But UVC ultraviolet rays, such as 275nm, have a much shallower propagation depth in adult epidermis. After penetrating the stratum corneum, more than 97% of the energy is absorbed, and the energy that ultimately penetrates the dermis layer is not even 0.1%. So, to be precise, UVC deep ultraviolet has little harm to human skin, while it is much more dangerous to the eyes without the stratum corneum. Of course, even the weakest light can be harmful to the human body if exposed for a long time
So don't blindly fear UVC deep ultraviolet rays, because short-term skin damage can be ignored; Don't risk yourself, staring at the LED will definitely cause eye injuries