Sunscreen: How Much Should You Apply?

It is recommended that you use sunscreen products regularly to reduce skin damage caused by the sun's UV rays. Excessive sun exposure is known to induce solar erythema, photocarcinogenesis (development of cancerous tumors) and photoaging. This is a process where the skin undergoes changes/damage: Increased epidermal thickness, pigment heterogeneity and degeneration of the elastic tissue of the dermis, degradation of collagen in the dermis, visible dilation of blood vessels under the skin and increased mutagenesis of keratinocytes and melanocytes in the skin. Thus, the best approach is to systematically apply sun protection or sunscreen, adjusted to the intensity of the radiation and the skin's phototype. The purpose of sunscreen products is to filter UVA and UVB rays. But how much sunscreen is recommended to use on your face or body?

Opting for a sunscreen with a high protection factor is not enough to protect you from the harmful effects of the sun's rays. You need to apply a sufficient amount of sunscreen, 2 mg per cm² of skin, to obtain the SPF value indicated on the label. This is equivalent to about 35 g of sunscreen for the entire body for an adult of standard height and weight. That's two 200 mL bottles of sunscreen per person per week.

Studies have shown that consumers only use about a quarter of this amount, or 0.5 mg per cm², in real life. However, the SPF on the label is related to the amount of product applied. This means that the SPF distributed on the consumer's skin is lower than expected. So, to avoid getting lost in the calculations and apply the right layer of sunscreen, you can help yourself with this recommendation:

• Apply the sunscreen along your finger before spreading it on different areas of the body. Use 2.5 fingers on the face and neck, 8 fingers on the torso and back, 4 fingers on each arm, 1 finger on each hand, 6 fingers on each leg and 2 fingers on each foot;

• Spread up to the equivalent of 7 teaspoons on all parts of the body;

• Apply between 12 and 15 sprays with spray sunscreens.

Thus, the application of a generous amount of sunscreen has proven to be by far the most important factor in having a good effectiveness of the product, as well as a good distribution of the application and a good absorption spectrum specific to the filter used. The more, the better.