Premature ageing, skin cancer, burns... The sun can prove dangerous for the skin, regardless of the weather and whether you are indoors or outdoors. That's why it's necessary to block all UV rays. Therefore, the daily use of a sunscreen is essential. Even though the importance of applying sunscreen every day seems to be understood by most people, questions still remain, particularly about its application: how to apply it correctly? How much to use? Which areas to cover?
How to apply sunscreen?
Published on May 25, 2025, by Stéphanie, PhD, Doctorate in Life and Health Sciences — 5 min of reading
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Sunscreen: What is its purpose?
Sunscreen products come in various forms: oil, lotion, cream, milk, gel... Their purpose is to filter the UV rays from the sun that penetrate the epidermis and dermis, thereby reducing their exposure to the skin. UVB rays, which are responsible for sunburn, act on the level of the epidermis. UVA rays, on the other hand, generate free radicals and cause cell damage leading to photoaging. Thus, sunscreens serve to prevent sunburn, and also minimise skin ageing and reduce the risk of skin cancer.
Sunscreen: How to apply it correctly?
When applying your sunscreen, the most crucial aspect is to apply the correct amount of product to ensure its effectiveness, as well as a good absorption spectrum specific to the filter used.
You must apply it in sufficient quantity, that is 2 mg per cm² of skin, to achieve the protection factor value indicated on the label. This quantity equates to approximately 35 g of sun protection over the entire body for an adult of standard size and weight, which is two 200 mL bottles of sunscreen per person per week.
Indeed, studies have shown that consumers only use about a quarter of this amount, that is, 0.5 mg per cm², in real life. However, the SPF indicated on the label is related to the amount of product applied. This means that the SPF spread on the consumer's skin is lower than expected.
After applying your sun cream, wait around twenty minutes before exposing yourself to the sun or layering other products on top. This is the time needed to create a protective barrier against UV rays. Following this, the application of your sun protection should be done approximately every two hours. Indeed, the value of the SPF decreases with the impact of environmental factors, such as perspiration, swimming, skin rubbing against the bath towel or sand, and photodegradation.
For enhanced protection of your skin, it is also necessary to apply sunscreen to areas such as the eyelids, nose, ears, lips, etc... areas that are often overlooked. Lastly, we advise you to select a sunscreen that is suitable for your skin type : fair skin requires a sun protection product with a high SPF, whereas a lower UV protection index is recommended for darker and tanned skin.
Tip : If you want to boost your protection, use a serum rich in antioxidants (vitamin C, ferulic acid, resveratrol, tocopherol, thyme essential oil, etc...) before your sunscreen. Indeed, this treatment will help to protect the skin against external aggressions (pollution, smoking, sun exposure, etc...) that promote the development of free radicals, responsible for photo-ageing. You can, for example, opt for our radiance serum highly concentrated in vitamin C (11%) and in Albizia julibrissin extract (3%).
Sources
LIPOZENCIC J. & al. Sunscreens : the ultimate cosmetic. Acta Dermatovenerologica Croatica (2003).
FWULF H. C. & al. The relation between sun protection factor and amount of sunscreen applied in vivo. British Journal of Dermatology (2007).
MOHAMMAD T. F. & al. Sunscreens and photoaging: a review of current literature. American Journal of Clinical Dermatology (2021).
