There is no way to determine by appearance whether a person has a sexually transmitted disease?

That's correct; sexually transmitted diseases (STDs) often do not show visible symptoms, making it impossible to determine someone's health status based solely on their appearance. Many individuals with STDs may be asymptomatic, meaning they exhibit no signs or symptoms. Regular testing and open communication are essential for sexual health, as relying on appearance can lead to misunderstandings and increased risk of transmission.