Hmmm...that I remember when my Doctor had me on TGel, he had mentioned that I needed to apply it once a day. If you've got a docs instructions, I'd say follow em.
Croat...it's NOT unhealthy....There is such a small amount of coal tar that it's nothing to be concerned about. This has been dabated to death.
back to the topic...Everytime I shampoo I do it twice. The first one is quick and gets rid of the excess oil and dirt. Now the second wash has a chance of penatrating a little better and do what it's supposed to do.