Please also be aware that something as simple as brushing your teeth or eating crunchy foods can cause scratches and scrapes on your gums... they may be so small that you don't notice them, but to a virus, they are like Grand Canyons. HIV can be contracted by oral sex if you have done anything at all that could scratch the lining of the mouth or the gums.
For some viral infections (HPV, herpes) nothing is required except contact with skin. For the bacterial infections, (syphilis, gonorrhea, chlamidia, and yes, even strep) saliva is most often not enough protection to prevent infection by oral sex.
Since I enjoy doing home improvement/construction projects and landscaping, I don't remember the last time my hands DIDN'T have scrapes and scratches... so I don't even do unprotected handjobs (except with my partner.) If you insist on protecting yourself but still want to have sex, find sex partners who have the same self-preservation instinct you do, and stay away from those who try to talk you out of taking precautions. Since some of these diseases are either disfiguring (like HPV or herpes) or deadly (like HIV), IMHO there is no such thing as "too careful."
