Information and Advice Sexually Transmitted Infections Syphilis Syphilis Syphilis is a bacterial infection that in the early stages causes a painless, but highly infectious, sore on your genitals or around the mouth. The sore can last up to six weeks before disappearing. Secondary symptoms such as a rash, flu-like illness or patchy hair loss may then develop. These may disappear within a few weeks, after which you'll have a symptom-free phase. The late or tertiary stage of syphilis usually occurs after many years, and can cause serious conditions such as heart problems, paralysis and blindness. The symptoms of syphilis can be difficult to recognise. A simple blood test can usually be used to diagnose syphilis at any stage. The condition can be treated with antibiotics, usually penicillin injections. When syphilis is treated properly, the later stages can be prevented.