All I can say is from watching a couple of different shows on TV, one in particular is "Man-Fire-Food"
They always light and use wood fires and wood coals, a lot of the time, I see them starting fires with oils, kerosene etc.
It does raise an eye brow with me, and I don't use liquids except for left over food oils and grease.
My guess is, it must be ok, and if you do use gel, just use enough to get something going.