Is it possible to tan in the shade?

Initially, it is important to understand the mechanism of tanning. When the skin is exposed to the sun’s UV rays, it reacts by activating melanin production in melanocytes. Melanin, the brown pigment that gives skin its colour, then migrates to the surface of the epidermis to colour and protect it. Indeed, melanin is not only aesthetic: it absorbs part of the UV to protect DNA, the cells, lipids and proteins in the skin. Despite this, it is useful to know that around 15% of UVB still manage to reach the basal layer and 50% of UVA reach the dermis.

If the weather is sunny, sitting in the shade does not fully protect us from UV radiation.

Indeed, elements that form part of our environment, such as sand, snow or the surface of water can reflect sunlight onto our skin. The skin then comes into contact with harmful UV rays, even when we are under a tree or beneath a parasol. It is therefore entirely possible to tan in the shade. However, the extent of tanning achieved depends on the type of shade present and on the environment’s capacity to reflect UV rays. The UV reflection index of several surfaces is presented in the table below for guidance.

It is also useful to know that a cloudy sky also casts shade without protecting the skin. Indeed, only large dark clouds are capable of blocking all UV rays. A mid-altitude cloud layer can only stop 30 to 60% of the rays from the sun. Moreover, if the clouds are white and scattered, UV rays will be reflected and the radiation will then increase by 10%.

A study carried out in Sacramento, California, using UV sensors placed at various locations, made it possible to quantify the radiation received in two common shaded scenarios. Scientists measured UV levels in the shade of a parasol and UV exposure in the shade of a tree, with sensors positioned in full sun and in these two shaded areas between 13:00 and 15:00, the period corresponding to the peak of solar irradiation.

The results showed that tanning under a tree remains possible, as approximately 5% of UV rays still reach the skin in this setting. Exposure is even more pronounced when tanning under a parasol: over 17% of UV penetrates the shaded area. These findings confirm that tanning in the shade is possible, but also to get sunburnt in the shade when the sun protection is insufficient.

These observations highlight that not all shaded areas provide the same level of photoprotection. A dense shade cast by a wall or roof effectively blocks the majority of direct solar radiation. Conversely, the dappled shade beneath a leafy tree, parasol or pergola allows a significant fraction of light to pass through, in addition to reflections from sand, water or concrete.

Thus, even without direct exposure to sunlight, the skin can continue to receive ultraviolet radiation and therefore tan in the shade.

Thus, since the sun’s UV rays can reach us when we are in the shade, it is essential to protect our skin in these conditions. Indeed, UV rays can cause irreversible damage, in addition to sunburn. They generate within our bodies free radicals capable of altering cellular membranes, as well as inducing changes in the genetic code, which can lead to mutations and even to the proliferation of cancerous cells. By altering the dermal structural proteins, the oxidative stress is also responsible for accelerating skin ageing.

It is therefore important to protect yourself from UV rays by applying a daily sunscreen with broad-spectrum protection to the exposed areas of your face and body. Also remember to wear sunglasses and a hat, as UV rays can also damage hair and the scalp. Finally, if you use clothing for protection, be sure to check the UPF (UV Protection Factor), which measures the fabric’s ability to block UV rays. For example, a UPF of 25 means the fabric allows only about 1/25 of UVA and UVB radiation to pass through.

• GLANZ K. & al. Prevalence of sunburn, sun protection, and indoor tanning behaviors among Americans: Review from national surveys and case studies of 3 states. Journal of the American Academy of Dermatology (2011).

• LINOS E. & al. Types of shade vary in protection just like sunscreens. JAMA Dermatology (2017).

• SIVAMANI R. K. & al. Quantification of ultraviolet (UV) radiation in the shade and in direct sunlight. Dermatology Online Journal (2019).

• KRUTMANN J. & al. Attitudes and behaviors regarding sun exposure in Japan compared to Europe and North America. The Journal of Dermatology (2024).