Rusketus

Rusketus is the Finnish term for suntan or tanning of the skin, the darker coloration produced by ultraviolet radiation from the sun or artificial tanning devices. It denotes both the process and the resulting brownish coloration.

Exposure to UVA and UVB triggers melanocytes in the epidermis to produce melanin, which migrates to surrounding keratinocytes and darkens the skin. The extent of rusketus depends on skin type (for example, the Fitzpatrick scale), the amount and duration of UV exposure, latitude and altitude, and the use of sunscreen or protective clothing. UVB mainly influences a lasting tan by stimulating melanin production; UVA contributes to immediate pigment darkening and to photoaging.

While a tan indicates some UV damage, excessive exposure increases the risk of sunburn, skin aging, and skin cancer. Protective strategies include broad-spectrum sunscreen with an appropriate SPF, wearing protective clothing, seeking shade, and avoiding tanning devices.

In Finland and other northern regions, rusketus is commonly associated with summer outdoor life and holidays, and can be viewed as a sign of health or vitality, though health authorities emphasize cautious sun exposure.