What std causes dry itchy skin?

Syphilis and hiv: Advanced HIV is associated with dry and itchy skin. Syphilis leads to a rash which can appear to be dry. However, dry and itchy skin is usually not from an std. If it is occurring is a small area, then a skin fungal infection could be the cause. If it affecting the whole body there could be a number of causes including dry air and the type of soap you are using.