HIV is found in the body fluids of an infected person. But only some fluids have enough HIV to infect someone else. In men these fluids are:

• blood
• cum and pre-cum
• anal mucus (the coating of the inside of the arse).
  
  

Spit, sweat and urine do not have enough HIV in them to infect someone. And once outside our bodies, HIV can’t survive for very long at all.

For HIV to get from one man to another, the infected body fluid has to enter the other man’s bloodstream.   

How HIV is passed on during fucking

If a man with HIV fucks a man who doesn’t have HIV without a condom and comes inside him, the virus in his cum can get into the other man’s bloodstream through the lining of his arse. That's because the lining of the arse is delicate and can tear easily and bleed. It can also absorb the virus. 

The positive man’s pre-cum also has virus in it, so pulling out before coming isn’t risk-free. 

If an HIV negative man is fucking a positive man, HIV in blood or anal mucus can get into his body through the foreskin or head of his cock. It can also enter his cock through the lining of his urethra (the pipe that piss comes down).

How HIV is passed on during oral sex

We think most guys who got HIV from oral sex got cum in their mouths while sucking off a guy with HIV. The risk is increased if the guy giving head has bleeding gums, mouth ulcers or a throat infection, as these all make it easier for the virus to get in. 

However, the risk of getting HIV through oral sex is far less than through anal sex.

Other factors that affect whether HIV is passed on

HIV isn’t actually as infectious as many other sexually transmitted infections (STIs). It isn’t automatically passed on every time a positive and a negative man have unprotected sex.

But there are factors that increase the risk of it being passed on:

• viral load
• STIs
• rough sex
• using poppers.
  
  

Viral load

The higher your viral load, the more virus is in your blood, cum, pre-cum and anal mucus, which means there’s more to pass on to someone else.

STIs

If the positive partner has another STI, his viral load may be high. If the negative partner has an STI, there can be ulcers or inflammation which makes it easier for HIV to get in.

Sex that causes bleeding

The rougher the type of sex, the more likely that your arse or cock will bleed, making it easier for HIV to get into the bloodstream. It’s not just fucking that makes an arse bleed. Fisting and sex toys can also cause damage and increase the risk of passing on HIV.

Poppers

Studies show that men who sniff poppers when getting fucked without a condom are much more likely to get HIV than men who get fucked without a condom but don’t sniff poppers. 

There are various reasons why poppers might have this effect:

• Poppers open blood vessels wider, causing more blood to go into the arse. This could make it easier for HIV to get through these blood vessels, especially if using poppers makes the inside of the arse more likely to bleed during anal sex.
• Men who use poppers might be more likely to have rougher sex (with more bleeding).
• Some researchers think poppers might weaken the immune system for a few days, leaving someone more open to picking up HIV. But others don't believe that poppers do this.
  
  

Condoms

Using condoms is the best protection against passing on HIV or picking up other STIs. We’ve put lots of tips on using condoms in our section on condoms.