condensation on paintwork

[citroen]

I get a lot of condensation on my internal window sills in spite of having double glazing.Where the wooden windowsill meets the framework of the double glazing,I get this condensation and it turns the white gloss paint black.Is there anything I can paint over the top of my white paint in this area to prevent this black appearing?I have to paint this area every springtime when the condensation stops.