A box of disposable gloves is a very good thing to have in your trunk/boot/whatever in case of emergency. Sure, you might need to deliver a baby, do dishes, or clean up corrosive waste, but more importantly, safer sex is better sex. So here is how to make a quick barrier for your new friend, at least until you get to know each other a little better.
One latex glove (vinyl, nitrile or neoprene will NOT work! They snap before they stretch.)
One pair of decent scissors
1. Cut the three middle fingers off one glove, leaving just the thumb and pinky.
2. Cut a line through the palm-side of the glove from the wrist/cuff to the finger hole.
3. Insert thumbs in two the remaining glove-fingers and stretch as seems appropriate.
Ta-Da! A lovely latex barrier.
4. Get busy.
Saran wrap works very well for in place of latex, especially as it can be torn off in as large or as small an area as is desired. This is probably the most popular barrier method for cunnilingus, for those both with and without latex allergies, because it is inexpensive and easy to obtain with minimal embarassment at the checkout counter.
Disposable Gloves made of vinyl or nitrile can be stretched rather awkwardly in a pinch, or used at double thickness, but don't cut them-it compromises their structure and they'll tear up.
*note, don't do this for someone with a known latex allergy. Rashes aren't sexy. Nope, not kinky either.
And it was incredibly irresponsible of me not to mention anaphylactic shock, because it is at best a scary an uncomfortable experience, and at worst, fatal. Also latex allergies can build up over time with repeated exposure.
As momomom points out: "Once an allergy is known this is more likely. A rash usually occurs on the exposure that makes the person realize they are allergic."