I knew it had to be the glycerin, since it was the only change I had recently made to my regimen. Research later revealed that glycerin may, in fact, cause headaches particularly when it is consumed. Consumed??? Obviously, I wasn't drinking the stuff. So, my next thought was that it was seeping through the pores in my scalp. But guess what? I was eating the stuff...in a sense.
I'm often doing two or three things while doing my hair and realized that my glycerin laced fingers probably touched my face at some point. It could have been a simple nose rub or scratching an itch on my face or touching things and forgetting to wipe them off after having products on my hands. Oh well, lesson learned.
Hair Gardening Tip: Always wash your hands after applying fertilizer to your garden. Even though it is a natural product that will eventually lead to a stronger, healthier yield, it's not always meant for ingestion and may be toxic to the rest of the plant. Think about it. Just because manure is good for your plants doesn't mean you should eat it.