What Happens to the Skin When We Are Exposed to the Sun

Donna con pelle chiara e con lentiggini in spiaggia



Exposure of the body to sunlight provides certain health benefits while also posing risks, through a process known as photoaging. One of the primary contributors to skin aging is exposure to ultraviolet (UV) rays, which are classified based on their wavelength as follows:

UV-A (320–400 nm): Long-wave rays capable of penetrating deep into the skin layers, damaging collagen and elastic fibers in the dermis.

UV-B (290–320 nm): Medium-wave rays that affect the outermost layers of the skin and are responsible for tanning, sunburns, and erythema.

UV-C (100–290 nm): Short-wave rays, the most carcinogenic, but fortunately almost entirely absorbed by the ozone layer and thus rarely reach the Earth’s surface.

Fortunately, UV-A rays, to which we are most frequently exposed, are also the least harmful. UV-B rays are most intense around midday, and UV-C rays are present only in negligible amounts due to atmospheric filtering.

What Happens to the Skin After Prolonged Exposure to UV Radiation?

Two main biological responses occur:

Oxidative stress
Inflammation

Oxidative stress arises when the balance between oxidative and antioxidant mechanisms in the body is disrupted, leading to the overproduction of reactive oxygen species (ROS), especially in fibroblasts and keratinocytes. ROS are by-products of mitochondrial activity and are among the key factors involved in skin aging. Their production increases when UV exposure accelerates the mitochondrial process of adding electrons to oxygen molecules. Excessive sunlight leads to a significant increase in ROS and a reduction in detoxifying enzymes, resulting in damage to proteins, lipids, and DNA.

Inflammation is induced by the heat generated through sun exposure, which triggers vasodilation, increasing blood flow and resulting in skin redness and inflammation.

The Beneficial Effects of Sun Exposure

Despite its risks, sunlight has positive effects on the body. It improves mood, promotes vitamin D synthesis, supports the immune system, and can be a beneficial adjunct in managing skin conditions such as dermatitis and psoriasis—though not during acute flare-ups.

Guidelines for Safe Sun Exposure

Avoid direct sun exposure during peak hours, especially midday
Apply a high-quality sunscreen at least 30 minutes before exposure and reapply every two hours
Avoid exposing affected skin areas to sunlight during the acute phases of dermatological conditions
Consume foods rich in antioxidants and vitamins, especially Vitamin C and E (antioxidants) and Vitamin A (helping absorb UV-B rays and protecting the skin from photo-damage)