Many drugs can increase your sun sensitivity and make you more prone to sun damage if you aren't using sunscreen. They are lots of potential troublemakers so be sure to check; some are:
antibiotics especially tetracycline and sulfa drugs
some over the counter painkillers such as ibuprofen and naproxen
acne treatments like accutane and tretinoin
many antidepressants
ACE inhibitors and diuretics
some cold and allergy meds
cat lover 
When I was young we used to go "skinny dipping"; now we just "chunky dunk" 
