I have fainted three times in my life in reaction to crystal energy. Twice at a store and once again when a shaman handed me her clearing crystal. That shaman called it crystal sensitivity. But since then, I've been afraid to handle clear crystals without grounding my self first. Ever heard of such a thing?
It sounds like you are extremely sensitive to high energy. Some crystals can have very high energy and can make you feel dizzy, nauseous, spaced out, or agitated. Each person has a different reaction, and it sounds like fainting is how your body reacts. Grounding is definitely a good thing for you to do. I recommend you wear a strong grounding crystal, like Black Tourmaline, every day to help you with this. You should also clear the crystal every day in the morning before you head out. I like to smudge Black Tourmaline with sage, but any method will help. It is possible to increase your tolerance for higher energies by exposing yourself to high energies gradually over time. Gradually increase the time spent with the crystal and eventually you will find that it doesn't cause the same reaction. If you choose to do this, please make sure you are in a "safe" space at home or with friends. I hope this is helpful. Please let me know if you have any questions. I hope your journey is blessed with Love and Light.
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Disclaimer: I must share the standard disclaimer that I am not a doctor and cannot give out medical advice. Crystals for healing should be used as a compliment to other therapies and not as a replacement for regular medical care.