Can't access variable from another script

When a player catches boost(additional life) I want to access my health script and add +1 to the currentHealth. It doesn’t work.
Here my boost life script:

    public GameObject particles;
	public bool isOnTrigger = false;

	void OnTriggerEnter (Collider other) {
		if (other.tag == "Player") {
			GameObject.FindWithTag("Player").GetComponent<PlayerHealth>().currentHealth+=1;
			GameObject part = Instantiate(particles,transform.position,Quaternion.identity)as GameObject;
			Destroy(part,2);
			Destroy (this.gameObject);
		}

	}
}

This is HealthScript attached to the player:

public int currentHealth;
	private int startHealth = 7;
	private GUIStyle styleForHealth;
	private GUIStyle healthBarBG;
	private float healthBarLength;
	private bool showHealthBar = true;


	void Start(){
		currentHealth = startHealth;
	}

	void Update () {
		var scoreScr = Camera.main.GetComponent<ScoreScript> ();
		currentHealth = startHealth - scoreScr.miss - scoreScr.crush;

		if (currentHealth > startHealth)
			currentHealth = startHealth;
		if (currentHealth < 0)
			currentHealth = 0;
		if (currentHealth<1) {
			GameObject.FindWithTag("Player").GetComponent<PlayerController>().canControl = false;
			Invoke ("LevelStart", 2);
		}
		healthBarLength = ((Screen.width / 4 ) /startHealth)*currentHealth;
		if (healthBarLength < 1) {
			showHealthBar = false;
			healthBarLength = 0;
		}
	}

	void LevelStart(){
		Application.LoadLevel (2);
	}
	void OnGUI(){
		InitStyles();
		GUI.Box (new Rect(Screen.width/2+195,10,Screen.width/4+10,30),"  ",healthBarBG);
		if(showHealthBar)
			GUI.Box (new Rect(Screen.width/2+200,15,healthBarLength,20),currentHealth+"/"+startHealth, styleForHealth);

	}
	private void InitStyles(){
		if( styleForHealth == null ){
			styleForHealth = new GUIStyle( GUI.skin.box );
			styleForHealth.normal.background = MakeTex( 2, 2, new Color( 0.4f, 0.8f, 0f, 1f ) );
		}
		if (healthBarBG == null) {
			healthBarBG = new GUIStyle(GUI.skin.box);
			healthBarBG.normal.background = MakeTex(2,2, new Color(0f, 0.4f, 0f, 1f) );
		}
	}
	private Texture2D MakeTex( int width, int height, Color col ){
		Color[] pix = new Color[width * height];
		for( int i = 0; i < pix.Length; ++i ){
			pix[ i ] = col;
		}
		Texture2D result = new Texture2D( width, height );
		result.SetPixels( pix );
		result.Apply();
		return result;
	}

Thank you in advance.

Any change to currentHealth (as in +1) would be lost since PlayerHealth Update() recalcs it every frame. You need to redesign that bit