Chemical sunscreens may only work for 1 hr and extra applications do not extend the time. Chemical sunscreens are associated with increased, yes increased, skin cancer. Physical sunscreens are best, titanium dioxide, or zinc oxide. Neutragena has a sensitive skin sunscreen the TD. Disadvantages are: 1. if sweat much, it will run off, and 2. a slight whitish caste to skin.

Alterative is use a long sleeve sun shirt. They have enough ventilation to wear up to 95F. Examples are Boure jersey and solumbra cycling shirt. The solumbra is SPF 30 and Bour3 is SPF 50. Don't forget to put lotions on your hands. These shirts are about 90 or $100. There are a couple sites that offer for about $60, but I don't know what they are like when riding with them.

Second alternative is to float riding time so it's when the sun is not up.