Why sexually transmitted infections sometimes affect the skin
Sexually transmitted infections are caused by bacteria, viruses, or other organisms that can spread through sexual contact. Depending on the infection, transmission may occur through contact with infected bodily fluids, mucous membranes, genital sores, or affected skin.
Some infections remain localized around the genitals or mouth. Others can affect multiple body systems and produce symptoms far from the original site of exposure.
Syphilis is one important example. It is a bacterial infection that can progress through several stages when left untreated. During its secondary stage, it may cause a widespread rash involving the torso, arms, legs, palms, or soles. The rash can be subtle or prominent, and it may appear alongside fatigue, fever, swollen lymph nodes, or other symptoms.
However, a widespread rash is not proof of syphilis. Conditions such as psoriasis, eczema, medication reactions, viral infections, and certain vascular disorders can also cause extensive skin changes.
Herpes simplex virus usually causes localized blisters or sores, particularly around the mouth or genital area, although symptoms vary. Human papillomavirus, commonly known as HPV, can cause genital warts rather than a generalized red rash. HIV may produce a rash during early infection, but the accompanying symptoms are nonspecific and cannot distinguish HIV from many other illnesses.
Mpox can also produce skin lesions following close physical contact, including sexual contact. These lesions may appear on the face, hands, trunk, genital area, or other locations. Because the presentation varies, clinical evaluation and appropriate testing are needed when mpox is suspected.