How can this be a STRAIGHT answer without talking about the
yuckiness of heterosex..

The passing of any bodily fluid or material from one
individual to another
This first and most basic practice includes virtually all sexual
activity, therefore, in order to engage in a normal sex life, one
must use circumspect caution about what activities are acceptable
and with whom.
If you have a lover and have known this person for a protracted
period and both of you have reasonable assurances that neither of
you have strayed to assignations with outsiders, and if you both
take HIV tests regularly (twice a year), then the liklihood that
that either of you will infect the other is virtually nil. But,
even in this very cautious hypothetical example you still could
contract type C hepatitis if your sexplay includes ingestion of
feces or vomit. Or, in a less extreme variant, a long dormant
herpetic infection might appear and transfer without notice.
The question naturally arises: "What are safe sexual practices?"
This is a tricky question to answer. The problem comes from the
mounds of legal liability that return to haunt anyone who has the
chutzpah to step forward and declare some practice to be safe.
There are many lists of do's and dont's that are so specific that
they can never address the plethora of human sexual experiences. In
practice, safety becomes a matter of common sense.
While oral sex, including the swallowing of semen, has lately been
considered by some authorities not to be a vehicle for HIV, urine
and blood may still cause infection.
[edit]
Engaging in sexual contact with multiple partners and with unknown
partners
The numbers will eventually get you. It's a lottery and you stand a
better chance of winning (losing really) if you have 365 entries a
year instead of 3 or 4. You need to pick your partners carefully,
and what you find out over cocktails in two hours will simply not
be enough information. Offering yourself as a Bukkake target in a
bath house may sound thrilling as a fantasy, but it brings real
dangers along for the reality ride. Of course, you might do stuff
like this for years with no adverse results. Some people buy
lottery tickets every week and never win either, but odds playing
is a form of gambling, and at least in Lotto, you are only out a
buck.
Next to masturbation, frottage (rubbing someones genitals through
the clothing) is the least dangerous activity. Manipulating another
person's genitals may not cause infection, but pre-ejaculate and
vaginal fluid may still be introduced into a partner's body. This
may not be a problem unless one has a cut or rash on the skin. This
can then become an access point to the circulatory system. Licking
and sucking are a major part of sex, and for the most part, healthy
saliva and a generous dose of stomach acid will act as a bar to
most viruses. However, activities such as flossing or brushing the
teeth can cause cuts in the gums, leaving a more direct route for
viruses to follow.
Everything discussed to this point simply requires your judicious
screening of the candidate for your sexual fun. It would not be
smart to tempt fate by giving head to a guy you just met on the day
you had a wisdom tooth extracted. However, most people get to play
at least to the oral stage without having to face death, if they
are careful.
After this, things get a bit dicey. Deposits into the vagina and
into the anal cavity are like injections into your body. These
areas are rich in blood vessels and are uniquely equipped to engage
in chemical transfers into the bloodstream. The penis is also a
blood filled organ that easily suffers friction injuries.
Ergo:
[edit]
Penetrating the vagina or anus without a condom
This is a premier way to transfer any STD. Latex and poly condoms
protect against HIV, genital herpes, and pregnancy. Natural
lambskin condoms (like Fourex Brand) are good only against
conception. Their membranes, however, may allow disease to be
passed. Many people engage in the practice of barebacking. It is
generally unsafe unless one knows the history of their partner.
Taking anything into your body, by mouth or other orifice,
compromises the integrity of your person. We take it so for granted
by breathing, drinking, eating all the time, that we are not
focused on the idea that we may be poisoned.