diff --git a/ProfanityFilter/ProfanityFilter/AllowList.cs b/ProfanityFilter/ProfanityFilter/AllowList.cs
index b3e1a4a..b321a0a 100644
--- a/ProfanityFilter/ProfanityFilter/AllowList.cs
+++ b/ProfanityFilter/ProfanityFilter/AllowList.cs
@@ -21,96 +21,97 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Globalization;
+using System.Linq;
 using ProfanityFilter.Interfaces;
 
 namespace ProfanityFilter
 {
-    public class AllowList : IAllowList
-    {
-        List<string> _allowList;
+	public class AllowList : IAllowList
+	{
+		HashSet<string> _allowList;
 
-        public AllowList()
-        {
-            _allowList = new List<string>();
-        }
+		public AllowList()
+		{
+			_allowList = new HashSet<string>();
+		}
 
-        /// <summary>
-        /// Return an instance of a read only collection containing allow list
-        /// </summary>
-        public ReadOnlyCollection<string> ToList
-        {
-            get
-            {
-                return new ReadOnlyCollection<string>(_allowList);
-            }
-        }
+		/// <summary>
+		/// Return an instance of a read only collection containing allow list
+		/// </summary>
+		public ReadOnlyCollection<string> ToList
+		{
+			get
+			{
+				return new ReadOnlyCollection<string>(_allowList.ToList());
+			}
+		}
 
-        /// <summary>
-        /// Add a word to the profanity allow list. This means a word that is in the allow list
-        /// can be ignored. All words are treated as case insensitive.
-        /// </summary>
-        /// <param name="wordToAllowlist">The word that you want to allow list.</param>
-        public void Add(string wordToAllowlist)
-        {
-            if (string.IsNullOrEmpty(wordToAllowlist))
-            {
-                throw new ArgumentNullException(nameof(wordToAllowlist));
-            }
+		/// <summary>
+		/// Add a word to the profanity allow list. This means a word that is in the allow list
+		/// can be ignored. All words are treated as case insensitive.
+		/// </summary>
+		/// <param name="wordToAllowlist">The word that you want to allow list.</param>
+		public void Add(string wordToAllowlist)
+		{
+			if (string.IsNullOrEmpty(wordToAllowlist))
+			{
+				throw new ArgumentNullException(nameof(wordToAllowlist));
+			}
 
-            if (!_allowList.Contains(wordToAllowlist.ToLower(CultureInfo.InvariantCulture)))
-            {
-                _allowList.Add(wordToAllowlist.ToLower(CultureInfo.InvariantCulture));
-            }
-        }
+			if (!_allowList.Contains(wordToAllowlist.ToLower(CultureInfo.InvariantCulture)))
+			{
+				_allowList.Add(wordToAllowlist.ToLower(CultureInfo.InvariantCulture));
+			}
+		}
 
-        /// <summary>
-        /// 
-        /// </summary>
-        /// <param name="wordToCheck"></param>
-        /// <returns></returns>
-        public bool Contains(string wordToCheck)
-        {
-            if (string.IsNullOrEmpty(wordToCheck))
-            {
-                throw new ArgumentNullException(nameof(wordToCheck));
-            }
+		/// <summary>
+		/// 
+		/// </summary>
+		/// <param name="wordToCheck"></param>
+		/// <returns></returns>
+		public bool Contains(string wordToCheck)
+		{
+			if (string.IsNullOrEmpty(wordToCheck))
+			{
+				throw new ArgumentNullException(nameof(wordToCheck));
+			}
 
-            return _allowList.Contains(wordToCheck.ToLower(CultureInfo.InvariantCulture));
-        }
+			return _allowList.Contains(wordToCheck.ToLower(CultureInfo.InvariantCulture));
+		}
 
-        /// <summary>
-        /// Return the number of items in the allow list.
-        /// </summary>
-        /// <returns>The number of items in the allow list.</returns>
-        public int Count
-        {
-            get
-            {
-                return _allowList.Count;
-            }
-        }
+		/// <summary>
+		/// Return the number of items in the allow list.
+		/// </summary>
+		/// <returns>The number of items in the allow list.</returns>
+		public int Count
+		{
+			get
+			{
+				return _allowList.Count;
+			}
+		}
 
-        /// <summary>
-        /// Remove all words from the allow list.
-        /// </summary>  
-        public void Clear()
-        {
-            _allowList.Clear();
-        }
+		/// <summary>
+		/// Remove all words from the allow list.
+		/// </summary>  
+		public void Clear()
+		{
+			_allowList.Clear();
+		}
 
-        /// <summary>
-        /// Remove a word from the profanity allow list. All words are treated as case insensitive.
-        /// </summary>
-        /// <param name="wordToRemove">The word that you want to use</param>
-        /// <returns>True if the word is successfuly removes, False otherwise.</returns>
-        public bool Remove(string wordToRemove)
-        {
-            if (string.IsNullOrEmpty(wordToRemove))
-            {
-                throw new ArgumentNullException(nameof(wordToRemove));
-            }
+		/// <summary>
+		/// Remove a word from the profanity allow list. All words are treated as case insensitive.
+		/// </summary>
+		/// <param name="wordToRemove">The word that you want to use</param>
+		/// <returns>True if the word is successfuly removes, False otherwise.</returns>
+		public bool Remove(string wordToRemove)
+		{
+			if (string.IsNullOrEmpty(wordToRemove))
+			{
+				throw new ArgumentNullException(nameof(wordToRemove));
+			}
 
-            return _allowList.Remove(wordToRemove.ToLower(CultureInfo.InvariantCulture));
-        }
-    }
+			return _allowList.Remove(wordToRemove.ToLower(CultureInfo.InvariantCulture));
+		}
+	}
 }
diff --git a/ProfanityFilter/ProfanityFilter/ProfanityList.cs b/ProfanityFilter/ProfanityFilter/ProfanityList.cs
index 9f49e42..c850d1d 100644
--- a/ProfanityFilter/ProfanityFilter/ProfanityList.cs
+++ b/ProfanityFilter/ProfanityFilter/ProfanityList.cs
@@ -17,6 +17,8 @@ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 */
+using System.Collections.Generic;
+
 namespace ProfanityFilter
 {
     /// <summary>
@@ -27,7 +29,7 @@ namespace ProfanityFilter
     /// </summary>
     public partial class ProfanityBase
     {
-        private readonly string[] _wordList =
+        private readonly HashSet<string> _wordList = new HashSet<string>()
         {
              "2 girls 1 cup",
              "2 girls one cup",