Help: My variable is always resetting to default value during play mode.

I have a simple script to keep track of a public HP variable and it also has a function Apply1Damage() that reduces HP by 1 everytime it is called. I also have a script which SendMessage() when a collision or a trigger is detected (OnTriggerEnter, OnCollisionEnter). I have applied the HP script to my enemies object and it works perfectly. However, when I apply the same script to my player object, the HP variable keep resetting to the initial value at a very fast speed. Using Debug.Log, I see that my player is receiving the damage and that the health variable is being reduced, but never less than the initial value-1. What could be causing this?

Here are the relevant scripts:

 public class DamageableMonster : MonoBehaviour {
 
     public float health;
     Animator damageableObjectAnimator;
 
     void Start()
     {
         damageableObjectAnimator = GetComponent<Animator>();
     }
 
     void apply1Damage()
     {
         health--;
         Debug.Log("Health down to: " + health);
     }
 
     void Update () {
         if (health <= 0)
         {
             damageableObjectAnimator.SetTrigger("Death");
         }
     }
 }

And

 public class Apply1Damage : MonoBehaviour {
 
     public float knockback;
     // Use this for initialization
     void Start () {
         knockback = 1000;
     }
 
     void OnCollisionEnter2D(Collision2D other)
     {
         if (other.gameObject.layer != 8)
         {
             Debug.Log("HIT");
             float xDistance = (other.transform.position.x - gameObject.GetComponentInParent<Transform>().position.x);
             float yDistance = (other.transform.position.y - gameObject.GetComponentInParent<Transform>().position.y);
             other.collider.SendMessage("apply1Damage");
             other.rigidbody.AddForce(new Vector2(xDistance * knockback, yDistance * knockback));
         }
     }
 
     void OnTriggerEnter2D(Collider2D other)
     {
         if (other.gameObject.layer != 8)
         {
             Debug.Log("HIT");
             float xDistance = (other.transform.position.x - gameObject.GetComponentInParent<Transform>().position.x);
             float yDistance = (other.transform.position.y - gameObject.GetComponentInParent<Transform>().position.y);
             other.SendMessage("apply1Damage");
             other.GetComponent<Rigidbody2D>().AddForce(new Vector2(xDistance * knockback, yDistance * knockback));
         }
     }
     
 }