I think I know the answer to this but I have a long 12 weeks ahead so was hoping I can get some insight that can keep me sane in the mean time. And advice on resuming sex with my partner, and keeping him safe. 

So I’m gay. And recently ended up drunk at a party i as usual was the last to leave. The host and I (someone I don’t know) ended up watching porn and masterbating or own penis. 

As usual this progressed to us touching each other’s penis (hand genital). 

Eventually when we was close to climax he stood up and climaxed over my face. Still no contact with his penis on my face/mouth but obviously a covering of sperm. 

Even in my drunken state I noticed what was happening and tried to keep my eyes and mouth closed. 

Unfortunately I wasn’t good enough and a tiny bit of sperm entered my mouth. I only noticed that some got in my mouth because of the taste. But I’m sure it can’t have been much the most of it was on the unbroken skin of my face. I immediately spat what I could out of my mouth. 

Unfortunately at the same time I have a cut on my lip, as well as two normal canker sores in my mouth one on my inner lip and one on my gum. 

Is this in anyway sufficient to spread Syphilis or HIV? 

You describe a very low risk exposure with little or no risk for either syphilis or HIV. Even direct ejaculation in the mouth carries little risk for HIV:  CDC has calculated an approximate risk of 1 in 10,000, which is equivalent to giving BJs to HIV infected men, with ejaculation in your mouth, once daily for 27 years before transmission of the virus might be likely. In general, semen does not transmit syphilis; and catching syphilis usually depends on infected material being massaged into exposed tissues. That's why the chancre of primary syphlis usually appears on sites of friction during sex -- penile shaft or head, vaginal or anal opening, etc. For these reasons, I would consider facial exposure to your partner's semen as having little or no risk, even if he has syphilis or HIV. It also was extremely low risk for gonorrhea and chlamydia, so I'm not surprised your oral tests for those STIs were negative.

Most STD clinics or other knowledgeable clinics routinely recommend HIV and syphilis testing whenever someone is at any risk at all, or when gonorrhea/chlamydia testing is done. They may agree that HIV and syphilis tests are optional and not really required, but nonetheless are following their routine testing procedures. Anyway, that certainly is my view and advice -- i.e. that syphilis or HIV testing really aren't necessary after the events you have described. If you do go forward with testing, the standard AgAb ("combo", 4th generation) HIV blood tests are conclusive by 6 weeks (and nearly conclusive at 4 weeks). The timing for syphilis testing is less clear:  6 weeks usually is enough, but many experts do recommend waiting until 8 or even 12 weeks.

In summary, your risk is so low that if somehow I were in your situation, I would not be tested at all, and I would continue unprotected sex with my wife with no worry of infecting her. If you do decide to get tested for either HIV or syphilis, I think you should continue sex with your regular partner in the meantime. The chance you'll have a positive result and need to break the news later is zero for all practical purposes.

One final option is to speak with your recent partner and discuss the possibility that both of you be tested now for HIV and syphilis. If both negative, as expected, you'll both know there was no risk for either of you.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD

I can’t believe a doctor would not be tested in my situation. That’s some vote of confidence. 

I’m trying to keep things off record so using online tests. Already set me back £100 and a further £20 for this consultation so if you really think it’s safe for me not to test again I won’t. 

I have read the 1 in 10000 for HiV from full oral sex. But figured direct semen onto my sore on my lips would increase that some what? But reading between the lines I’m actually at less risk as I didn’t have his penis in my mouth. 

Can I just clarify syphillis just with you saying “in general it’s not spread via semen” in what situation is it spread via semen because I think rather than testing I’ll just keep an eye on my hands for a unexplained sore as this is the only part of my body that touched him. 

Anyway if you think it’s safe to not test and move on and we can say this with pretty much certainty I’ll do that. Thanks 

Having some sort of sore in your mouth would not materially elevate the risk of HIV. If you think about it, at any point in time a fair number of people have canker sores, inflamed gums, outbreaks of oral herpes, etc. So the 1 in 10,000 risk estimate can be considered to take this into account. A basic fact of HIV transmission is that it requires large amounts of virus to come into direct contact with susceptible cells. "Just one virus" doesn't do it; in this respect HIV is very different than, say, measles or norovirus (the main cause of viral gastroenteritis). Even with direct ejaculation of HIV infected semen into the rectum, for example, the chance the exposed person will be infected is around once for every 1,000 exposures.

I am unaware of any circumstances in which semen would transmit syphilis. I suppose there could be some low risk if there were a chancre at the urethral opening, but even then the chance of transmission would be minuscule. And see my comment above about massaging syphilis bacteria into susceptible tissues.)

I do think it is safe not to test, if you are confident the psychological (worry avoidance) rationale doesn't apply to you.

Just as a by the way - and how my mind is rationalising it (maybe it would help others) I would imagine any STI would be far more common if things like hand-genital contact and tiny amounts of semen come into contact with you spread infection. 

I paid my money to ask you my thoughts and you are saying not to test. I’d be silly not to listen. I’ll move on without STD worries. 

Thanks again and goodbye.