There are some precautions that you can reduce the chances of skin diseases..
-Sun's rays are strongest during 10 am to 4 pm,try to avoid outdoor activities during these time.
-Use a sunscreen with SPF 3 or higher before you go out.
-Wear long sleeve cloths to protect exposed skin
-Wear a UV blocking sun glasses.
-Use a lip balm that contains sun screen.
We cannot say fully that it is because of the sun rays. Nutritional deficiency,the food we consume on a daily basis has changed vastly.Also protection from ultra violet rays is very important