Health System..?

My health system isn't working. It's supposed to when the enemy enters the trigger, take 1 point off of your health, and ignore collisions between the enemy and you for 3 seconds- however, nothing is happening at all.

Here's the script on the trigger child of the main character:

var ColliderObj : GameObject;

function OnTriggerEnter(other : Collider) {
    if (other.CompareTag("Enemy")) {
       /// Calls the function ApplyDamage with a value of 5
gameObject.BroadcastMessage ("ApplyDamage", 1);
Physics.IgnoreCollision(ColliderObj.collider, other.collider);
yield WaitForSeconds(3);
Physics.IgnoreCollision(ColliderObj.collider, other.collider, false);
}

}

and here's the one on the parent object :

var hitPoints = 3;
var leveltoload = 1;
function Start(){
hitPoints = 3;
}
function Update(){
print(hitPoints);
}
function ApplyDamage (damage : int) {

    if (hitPoints <= 0)
        return;
    if(hitPoints == 0)
    Die();
    hitPoints -= damage;

}
function Die(){
Application.LoadLevel(leveltoload);
}

Help!

You are broadcasting the message to the wrong gameObject. You have to write

var ColliderObj : GameObject;

function OnTriggerEnter(other : Collider){
    if (other.CompareTag("Enemy")) {
       /// Calls the function ApplyDamage with a value of 5

// here is your mistake.
other.gameObject.BroadcastMessage ("ApplyDamage", 1);

Physics.IgnoreCollision(ColliderObj.collider, other.collider);
yield WaitForSeconds(3);
Physics.IgnoreCollision(ColliderObj.collider, other.collider, false);
}

}

other.gameObject is your enemy. gameObject is the object the script is attached to.