Which std is contagious through skin contact ?

Herpes ; Syphilis: Herpes and syphilis.

Genital warts: Also genital warts (hpv) - although there is now a vaccine to prevent some strains of hpv, not everybody get immunized.

Syphilis, HSV, HPV: Ii agree with other replies (greetings to Bob Killian!): The main STDs transmitted skin to skin are syphilis, herpes, and HPV. But ithis doesn't mean any skin contact is a risk. Even with direct genital skin contact, such as genital apposition without penetration,is low risk. Almost all patients with these STDs have had unprotected vaginal, anal, or sometimes oral sex with infected partners.