... humans couldn't go into sunlight

You all know the stories about Dracula and other vampires. They can't go into the sun, otherwise they will die. But what would happen, if all human being would be allergic to the sunlight and couldn't spend time in the sun.

If we couldn't go into the sun, we would have to change our life completely. First of all, it would be more practical to switch our sleeping and waking rhythm. Instead of staying awake during the day, we should sleep. Then we could use the sun free nights for being awake. It would allow us to move outside freely without being worried about getting into contact with sunlight. This would lead to some other problems. In the nights without the sun it is often very dark. That means, we have to lighten up everything we want to see. We could do that by putting streetlights or floodlights everywhere. An other idea would be to give everyone a night vision goggle. That would save energy. A combination of both would probably be the best. Popular and frequently used spaces as city centers, school yards, playgrounds, etc. should have floodlights, while everyone still has night vision goggle for the remaining dark spaces. Nevertheless, a lot more energy would be necessary, because of all the lights.

During the summer the days become longer, and the sun shines for more hour a day. But if summer is in the northern hemisphere, in the southern is winter. For the humans it would be more practical to live in the areas with more night, because then they can leave the house more often without the sun shining. Perhaps there would be the development of moving with the seasons. From around October to March all the humans live on the northern hemisphere and during the other months from April to September in the southern hemisphere. Also, it would be good to live close to the poles. At the polar circles there is every year one day completely without sun and another without darkness. Even more in the north for the northern hemisphere and even more in the south for the southern hemisphere it is even extremer. At the north pole during the winter months there is no sun at all, when in the summer the sun never sets. To avoid the sun the best, we should live half a year at the north pole and the other half of the year at the south pole. But of course there is not enough space for everyone. So the humanity would have to come up with other ideas.

For example a sun protection suit. The suit must cover the complete body of the person and must keep away all the light and radiation of the sun. Those protection suits would be dark and very warm. Living on earth wouldn't be the same only by night or with protection clothes.