The sun doesn't hurt and doesn't warn: ultraviolet radiation is invisible and cannot be felt at the moment of exposure. A person notices the consequence — redness, a burn, and over the years — chronic skin changes. Below is what is proven about the sun.
What ultraviolet radiation is and its ranges
Ultraviolet is radiation invisible to the eye, lying between visible light and X-rays, conventionally from 400 to 10 nanometers. The region is conventionally divided into long waves of 315–400 nm, medium waves of 280–315 nm, and short waves of 10–280 nm. Only the long-wave part — above 290 nm — reaches the Earth's surface; shorter waves are absorbed by ozone and oxygen. Ultraviolet radiation is carcinogenic to humans.
The level depends on the height of the sun, the season, latitude, altitude above sea level, the ozone layer, and reflection: water, sand, and fresh snow intensify exposure. Under cloud cover, the ultraviolet level can remain high. Climate change, through fluctuations in the ozone layer and cloudiness, is projected to affect ultraviolet levels near the Earth's surface.
UV index and sunscreens
The UV index describes the level of solar ultraviolet radiation near the Earth's surface and indicates the potential for skin damage: the higher the value, the greater the potential for harm. Protection is recommended starting at 3 and above. A broad-spectrum product is applied to areas not covered by clothing; it is not intended to extend time in the sun. Shade and clothing provide more reliable protection than the product alone.
What is proven: photoaging and skin cancer
Acute effects include DNA damage, sunburn, phototoxic and photoallergic reactions, and immune suppression. Immunosuppression is considered a cancer risk factor and can reactivate viruses, such as herpes on the lips.
Chronic effects include melanoma, squamous cell and basal cell carcinoma, and premature aging: loss of elasticity at a young age and slowed healing. Melanoma is a life-threatening malignant cancer; squamous cell carcinoma usually spreads less and less often leads to death, while basal cell carcinoma grows slowly and occurs mainly in older people. In 2020, more than 1.5 million skin cancers were diagnosed worldwide, with more than 120 thousand deaths associated with them; about 1.2 million new non-melanoma cancers and 325 thousand melanomas. Due to excessive ultraviolet radiation that year, there were 64 thousand premature deaths from non-melanoma cancers and 57 thousand from melanoma.
Eyes: acute inflammation of the cornea or conjunctiva; chronically — cataract, pterygium, cancer around the eye. Of the 15 million cases of blindness due to cataract, approximately 10% may be linked to ultraviolet radiation. Ultraviolet radiation may also be linked to the development of age-related macular degeneration.
Facts about "safe" tanning
Artificial tanning increases the risk of skin cancer and is not considered a way to achieve a sufficient level of vitamin D; some countries have already restricted tanning beds by law. A small amount of ultraviolet radiation is beneficial and necessary for vitamin D, but excessive amounts are not. Skin cancer is largely preventable.
What reduces risk
Risk is reduced by shade and clothing with long sleeves, a wide-brimmed hat for the face, ears, and neck, and close-fitting glasses that protect from the sides, with 99–100% protection against UV-A and UV-B. Limiting time in the midday sun is also part of prevention measures.
Children specifically: their skin and eyes are more vulnerable, and burns in childhood increase the risk of cancer later in life; a larger share of radiation reaches a child's retina. Fair-skinned people burn more severely and have a higher risk of skin cancer than dark-skinned people, but skin cancer also occurs in dark-skinned people.
When to see a doctor
Higher-risk groups include:
- people with a large number of nevi;
- people with a family history of skin cancer;
- those taking medications that increase sensitivity to the sun;
- those who work outdoors.
In these groups, the risk of skin cancer is higher than in other people; the need for monitoring is determined by a doctor.
When to see a doctor immediately: if the condition is life-threatening — for example, signs of a stroke or heart attack — call 103 or 112. This is a case when an ambulance comes rather than waiting for an appointment.
This material is for reference: it describes the mechanism and protection but does not replace consultation with a doctor who sees your skin.
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This content is for reference and does not replace a doctor's consultation. Medical disclaimer