Unprotected sun exposure does a number on the skin. “The DNA in skin cells gets damaged when the skin is unprotected and exposed to UVA and UVB radiation from the sun,” explains Jodi LoGerfo, DNP, who is a doctor of nursing practice and a family nurse practitioner certified in family medicine and dermatology. The damage done to the DNA can result in premature aging, as well as skin diseases and even cancer.

But it can also deplete your skin of moisture, degrade the lipid barrier, and even alter the microbiome. 

High temperatures and sun can cause moisture in the skin to evaporate into the air around it, an occurrence called transepidermal water loss. As the water leaves the skin, the epidermis dehydrates and can appear ashy and parched.

The heat and UV rays also damage the skin’s natural oils. The skin’s moisture barrier is made up of lipids and fatty acids that create a seal, which helps keep moisture trapped in the dermis. When the moisture barrier is damaged, it can lead to a scaly, cracked appearance—as well as increased irritation and sensitivity. 

Finally, research shows that sun damage can even alter the microbiome2. The skin microbiome plays an important role in your body’s immune function. And exposure to unprotected UV radiation can cause changes in how that immune function works—although researchers note that more studies are needed to determine how and to what extent.