<human>:  Why did the Prussian king Frederick the Great have a bald head?
<bot>: Frederick the Great was bald because he had a dreadful disease called syphilis. Syphilis is a bacterial infection that causes the body to react to it by creating a rash, which can lead to hair loss. Syphilis is very contagious, and it was a common problem in Europe during the 18th century. It is estimated that at least 25% of people in Europe had syphilis at the time, and it was one of the most common causes of death among the nobility.