"Any creature striking the character with its body or handheld weapons deals normal damagebut at the same time the attacker takes 1d6 points of damage +1 point per caster level."
Meaning that you don't take damage unless you do it.
This is how the game works. If you attack someone and hit them it means you overcame thier armor class. The spell does not say, "if you strike a creature, or roll high enough to hit with a touch attack you take damage", it says when you deal damage you take damage at the same time.
It could even be said that a touch attack that didn't deal damage wouldn't activate the shield, since the you aren't dealing damage (which is the point at which you take damage), though I don't think that was the intent of the spell.
And just in case you don't believe me:
PHB p279
hit: Make a successful attack roll.
Meaning that you don't take damage unless you do it.
This is how the game works. If you attack someone and hit them it means you overcame thier armor class. The spell does not say, "if you strike a creature, or roll high enough to hit with a touch attack you take damage", it says when you deal damage you take damage at the same time.
It could even be said that a touch attack that didn't deal damage wouldn't activate the shield, since the you aren't dealing damage (which is the point at which you take damage), though I don't think that was the intent of the spell.
And just in case you don't believe me:
PHB p279
hit: Make a successful attack roll.