Local anesthesia makes me feel faint. i even passed out once, even though i felt no pain or anxiety. now it does not numb me very much at all. this has happened with many different dentists. why?

Different anesthetic: There are many diff anesthetics available. Some more effective than others. Have your dentist try different ones to see which works best for you.

Dr Grossman agreed

Strong emotions: Emotions have much to do with your experiences and sedation may be necesary for a pleasant dental visit. I would also try differing anesthetics with nitrous oxide until a safe and pleasant visit is possible. You can have a good experience...

Different anesthetic: First, fainting from anesthetic injections without anxiety is usually caused by 2 things, Epinephrine in the anesthetic and- or injecting too fast. Secondly, not getting numb could signify another type of anesthetic should be tried!

Faint: No pain or anxiety, but there is stress. It may be a vagal reflex with psychological trigger. Not numbing is because the doctors eliminate the epinephrine, so the local anesthetic is taken away by the usual metabolism . You may have a high blood supply in the area. Theoretically, the receptors of sodium might be altered as other possibility ( never proven scientifically).

Some thoughts-: Nerves can't be immune to the effects of local anesthetics. There are certain variables that can have an effect- your "perception", emotions, subconscious thoughts, infection, poor technique, additional nerves not anesthetized, nerves not in their usual place (anatomy), etc. Perhaps you just haven't found the right dentist yet.

Dr Del Valle agreed

See below: This may be true but not related. Some patients are indeed resistant to local anesthetics, and there are alternatives that can be tried. There are people who have an adverse physiologic reaction to needles, I am one, and get faint or pass out when they are used. Talk to your dentist about alternatives.

Inform : Dentist about this, and any other doctor that plans on using local for you. There are certain local anesthetics that dentists reach for when dealing with pts that are resistant to the usual local anesthetic.