There is a risk of HIV transmission from fisting if the fister (the guy doing the fisting) has cuts or sores on his hand or wrist. If the guy getting fisted is HIV-positive, HIV in his anal mucus (the stuff that lines the arse) or any blood inside his arse could get into the bloodstream of the fister through the cuts or sores on his hand. If the fister has HIV, infected blood from the cuts could be absorbed into the bloodstream of the guy getting fisted through the lining of his arse. However, the likelihood of this happening is very low.

If more than one person is being fisted, in a group sex scene, HIV or hepatitis C could be passed from one fistee (the guy getting fisted) to another, via anal mucus or blood carried on the fist.

It is also possible to acquire a variety of gut infections, if traces of faeces get passed to the mouth. When fisting, sharing a pot of lube with a partner can also lead to the transmission of HIV and other STIs, including hepatitis C, as the pot of lube can become contaminated with blood or anal mucus.

Using gloves, such as Marigold extra thins or surgical gloves, can cut the risk of most infections if a new pair is used with each sexual partner. It is easy to damage the lining of the arse when fisting, so if fisting is followed by fucking without a condom then transmission of HIV to either partner is more likely.

Using oil-based lube (such as Crisco) for fisting will create additional risks if you then choose to fuck afterwards, as the oil in the lube will damage most condoms. If you think it is likely that you will fist and fuck, use water-based lubricant to fist or use a non-latex condom which will not be damaged by oil (like polyurethane condoms) to fuck.