Tanning is the result of the body's exposure to the sun's UV rays. However, these rays can sometimes be reflected by certain objects or materials in our environment, and can then be projected into a shaded area. In this case, is it possible to tan in the shade?
Can we tan in the shade?
Published on October 4, 2024, by Pauline, Chemical Engineer — 4 min of reading
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Why does the skin tan in the shade?
When the skin is exposed to the sun's UV rays, it responds by stimulating the production of melanin by the melanocytes. The melanin then migrates to the surface of the epidermis to colour and protect it: this is tanning. If the weather is sunny, sitting in the shade does not completely shield us from UV rays.
Indeed, elements that are part of our environment, such as sand, snow or the surface of water can reflect sunlight onto our skin. Consequently, our skin comes into contact with harmful UV rays, even when we are under a tree or an umbrella. Therefore, it is entirely possible to tan in the shade. However, the extent of the tan achieved depends on the type of shade present and the environment's ability to reflect UV rays. The UV reflection index of some surfaces is presented in the table below.
| Surface | UV Ray Reflection Index |
|---|---|
| Sand | 20 % |
| Water | 10% - 30% |
| Sea Foam | 25 % |
| Snow | 85 % |
| Concrete | 10 % |
Note : it's important to understand that a cloudy weather also creates shade but does not necessarily protect the skin. Indeed, only large dark clouds are capable of blocking all UV rays. A layer of medium altitude cloud will only be able to block 30 to 60% of the rays from the sun. Furthermore, if the clouds are white and scattered, the UV rays will reflect and the radiation will then increase by 10%.
Even in the shade, protection is necessary.
Thus, since UV rays from the sun can reach us even when we are in the shade, it is important to protect our skin under these conditions. Indeed, UV rays can cause irreversible damage. They generate free radicals in our body that can alter cell membranes, but also induce changes in the genetic code, which can lead to mutations or even the proliferation of cancerous cells.
Finally, free radicals can also denature certain proteins essential to the skin. Penetrating to the dermis, UVA rays stimulate the ageing of the skin and promote the appearance of wrinkles, fine lines and pigmentation spots. UVB rays, on the other hand, cause skin burns, such as sunburn or more serious conditions (skin cancers).
Therefore, it is crucial to protect oneself from UV rays by applying a broad-spectrum sunscreen daily to the areas of the face and body that are exposed. Also, consider wearing sunglasses and a hat, as UV rays are also harmful to the hair and scalp. Finally, if you use loose clothing for protection, remember to check their UPF rating (UV Protection Factor), which measures their ability to block UV rays. For instance, a UPF rating of 25 means that the fabric only allows approximately 1/25 of UVA and UVB radiation to pass through.
Source
LEACHMAN S. & al. Slip versus slop: a direct comparison of UV-protective clothing to sunscreen. Cancers (2022).
