The important lesson is that infections can affect the skin in different ways. A rash on the lower legs is not automatically evidence of a sexually transmitted disease, and the absence of genital symptoms does not rule out an STI.
Why symptoms may appear long after exposure
One reason STI-related symptoms are frequently misunderstood is that infections do not always produce immediate warning signs.
The interval between exposure to an infectious organism and the development of symptoms is called the incubation period. This period varies considerably. Some infections produce symptoms within days, while others may take weeks or longer. Certain infections can remain asymptomatic for months or years.
Syphilis illustrates this problem particularly well. Its initial sore may be painless and located somewhere difficult to see. The sore can disappear without treatment, even though the infection remains in the body. A later rash may appear after the person has already forgotten about the original symptom.
Other infections can remain unnoticed because symptoms are mild, intermittent, or absent. A person may feel completely healthy while an infection is still present.