Cumulative overexposure to the sun and repeated sunburns play a major role in the development and aggravation of rosacea. The National Rosacea Society found that sun exposure was the biggest factor in triggering rosacea, the next being stress.
While UV overexposure is a well-known rosacea trigger, the how and why (histopathology) behind it is not. The heat from the sun, repeated sun exposure and sunburns cause capillaries to dilate and trigger rosacea symptoms. Any abrupt changes in temperature, including cold and wind aggravate rosacea as well.
UV rays damage the dermal matrix (the layer of skin beneath the epidermis) and can also cause rosacea due to disorganization and break down of vital proteins (elastin and collagen).
Elastin provides skin and capillaries with an ability to stretch and bounce back while collagen provides the structure for the skin and capillary walls, the supporting vessels to the skin. When these important proteins break down, the capillary walls lose the ability to “bounce back,” which contributes to permanent dilation, a key rosacea symptom. Elastin break down, known as elastosis, occurs with the influx of elastase that follows UV overexposure.
UV radiation penetrates easily to deeper layers in fair-skinned individuals and induces production of VEGF (vascular endothelial growth factor), which regulates blood vessel growth. This growth factor is linked to the development of dilated blood vessels or capillaries and may increase interleukin 8, which plays a role in inflammation, a key rosacea trigger.