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

That's correct; many sexually transmitted diseases (STDs) can be asymptomatic, meaning individuals may not show any visible signs or symptoms. Even if symptoms are present, they can vary widely and may not be easily recognizable. Therefore, the only reliable way to know if someone has an STD is through medical testing, not by their appearance. Regular testing and open communication about sexual health are essential for prevention and treatment.