If you are taking medications, birth-control pills, or using certain cosmetics you risk an increased sensitivity to the sun and a possible allergic reaction when using sunscreen. Check with your doctor or dermatologist for advice. Clothing is no guarantee of sun protection. Loose weaves still allow dangerous burning rays through. Fair-skinned people should apply sunscreen even under their clothing.
Overcast days are no guarantee of sun-protection.
The sun's rays are just as damaging and sunscreens are still a must. Be happy with your natural skin color. Tanning parlors can increase your risk of skin cancer. The higher you climb, the more intense the sun's rays become since there is less atmosphere to diffuse the damaging rays. Pile on the sunscreen.