Hamburg - It is impolite not to allow a person you are talking with to look you in the eye. 

Thus, the bad habit of not taking one's sunglasses off, particularly when entering an enclosed space, should stop, said Gabriele Krischel of an international network of etiquette trainers based in Hamburg. 

"My conversation partner should always have the opportunity to look me in the eye," said Krischel. 

Not many people follow the rule in the summer months when sunglasses are constantly worn, Krischel has observed. Sunglasses should not cover the eyes, at least not when striking up a conversation. 

"An exception is when the sun irritates the eyes so badly it could keep you from having a conversation," said Krischel. "Simply say sorry and explain that the sun is so blinding as you put on your sunglasses." (dpa)