This is most likely a polymorphous light eruption (PMLE) which is a reaction/allergy to UVA from sunlight. This rash usually appears some time after exposure to the sun and will subside over a few days or a couple of weeks. It usually happens when people go on vacation and have their first exposure to the sun after winter. It often gets better as the summer progresses. You should use good broad spectrum sunscreen. (Some examples of sunscreen with broad UV spectrum protection are Ombrelle or Anthelios 60). You can find more information about sun screens at http://www.skincareguide.ca/tf/content.asp?z=504. Disclaimer: This information is intended for informative purposes only; and is not intended to replace, in any way, the medical advice that can be provided by a physician or other medical professional. Please consult your physician with any questions or concerns you may have regarding your health.