GUI text not updateing

I'm trying to do a health system via GUItext heres the code I have for the GUIText its in java script but here

 var score = 0;
 function Update () {
 var text = "Health: ";
 guiText.text = text + score.ToString();
 }

and heres the code I have for when the zombie collides with the player

 var score = 1; 
 var GUIhealth : GUIText;
 
 function OnTriggerEnter( other : Collider ) 
 { 
 if (other.tag == "zom") 
 {
 score++; 
 GUIhealth.text = score.ToString();
 } 
 }

but the text isnt updateing when the zombie hits the player the gui text is named GUIhealth but it isnt working:/ what am I doing wrong?