<div>
Would have written one but found this 

<pre><code class="code-10 nolinks" id="code-20-42390333-1">Function RemoveDuplicates(str)
 If Trim(str) = &quot;&quot; Then
 RemoveDuplicates = Array()
 Exit Function
 End If

 Set d = CreateObject(&quot;Scripting.Dictionary&quot;)
 d.CompareMode = vbTextCompare 'make dictionary case-insensitive

 For Each elem In Split(str, &quot;,&quot;)
 d(elem) = True
 Next

 RemoveDuplicates = d.Keys
End Function
</code></pre>
<a href="https://stackoverflow.com/questions/20310609/how-to-remove-duplicates-from-an-array" rel="ugc">https://stackoverflow.com/questions/20310609/how-to-remove-duplicates-from-an-array</a>
</div>

<div>
Add a sheet called &quot;Helper&quot; to your workbook and then run this macro. You can hide the Helper sheet if you like. 

<pre><code class="code-10 nolinks" id="code-20-42390335-1">Sub DeleteWithinComma()
Dim lngLastRow As Long
Dim lngRow As Long
Dim lngRowH As Long
Dim strWords() As String
Dim strParts() As String
Dim lngIndex As Long
Dim lngIndex2 As Long
Dim wsH As Worksheet

Set wsH = Sheets(&quot;Helper&quot;)
Const DATA_COL = &quot;A&quot; ' Change as needed
Const FIRST_ROW = 1 ' Change as needed

lngLastRow = Range(DATA_COL &amp; &quot;1048576&quot;).End(xlUp).Row

For lngRow = FIRST_ROW To lngLastRow
 wsH.UsedRange.ClearContents
 strWords = Split(Trim(Cells(lngRow, DATA_COL)), &quot;,&quot;)
 For lngIndex = 0 To UBound(strWords)
 strParts = Split(Trim(strWords(lngIndex)))
 For lngIndex2 = 0 To UBound(strParts)
 wsH.Cells(lngIndex2 + 1, &quot;A&quot;) = Trim(strParts(lngIndex2))
 Next
 On Error Resume Next
 wsH.Range(&quot;$A$1:$A$&quot; &amp; wsH.UsedRange.Rows.Count).RemoveDuplicates Columns:=1, Header:=xlNo
 strWords(lngIndex) = &quot;&quot;
 For lngRowH = 1 To wsH.UsedRange.Rows.Count
 strWords(lngIndex) = strWords(lngIndex) &amp; wsH.Cells(lngRowH, &quot;A&quot;) &amp; &quot; &quot;
 Next
 Next

 
 Cells(lngRow, DATA_COL).ClearContents
 For lngIndex = 0 To UBound(strWords)
 Cells(lngRow, DATA_COL) = Cells(lngRow, DATA_COL) &amp; strWords(lngIndex) &amp; &quot;, &quot;
 Next
 Cells(lngRow, DATA_COL) = Left(Cells(lngRow, DATA_COL), Len(Cells(lngRow, DATA_COL)) - 2)
Next
End Sub
</code></pre>
</div>

<div>
martin, that did not work. &nbsp;it seemed to have wiped entire workbook 
 
other guy, that removed all but one entry
</div>

<div>
<blockquote>
it seemed to have wiped entire workbook
</blockquote>
That didn't happen for me so try it with this workbook. 
 
Edit: I'm going to a play and dinner so I won't be available for several hours. 
<a href="https://filedb.experts-exchange.com/incoming/2017/12_w49/1213560/29071633.xlsm" target="_blank" class="file-inline" title="29071633.xlsm (18 KB)"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path d="M67.508 468.467c-58.005-58.013-58.016-151.92 0-209.943l225.011-225.04c44.643-44.645 117.279-44.645 161.92 0 44.743 44.749 44.753 117.186 0 161.944l-189.465 189.49c-31.41 31.413-82.518 31.412-113.926.001-31.479-31.482-31.49-82.453 0-113.944L311.51 110.491c4.687-4.687 12.286-4.687 16.972 0l16.967 16.971c4.685 4.686 4.685 12.283 0 16.969L184.983 304.917c-12.724 12.724-12.73 33.328 0 46.058 12.696 12.697 33.356 12.699 46.054-.001l189.465-189.489c25.987-25.989 25.994-68.06.001-94.056-25.931-25.934-68.119-25.932-94.049 0l-225.01 225.039c-39.249 39.252-39.258 102.795-.001 142.057 39.285 39.29 102.885 39.287 142.162-.028A739446.174 739446.174 0 0 1 439.497 238.49c4.686-4.687 12.282-4.684 16.969.004l16.967 16.971c4.685 4.686 4.689 12.279.004 16.965a755654.128 755654.128 0 0 0-195.881 195.996c-58.034 58.092-152.004 58.093-210.048.041z"/></svg>29071633.xlsm</a>
</div>

29071633.xlsm

EE29071633.xlsm

<div>
Hi, 
 
you can attempt to insert the word in a collection, if it fail, it is a duplicate:
<pre><code class="code-10 nolinks" id="code-20-42390443-1">Option Compare Database
Option Explicit
Option Base 0

Public Function removeDuplicateWords(ByVal strIn As String)
 Dim data() As String
 Dim strOut As String
 Dim i As Long
 Dim col As Collection
 
 data = Split(strIn, &quot;,&quot;)
 Set col = New Collection
 For i = LBound(data) To UBound(data)
 If Not (existInCollection(Trim(data(i)), col)) Then
 col.add Trim(data(i)), key:=Trim(data(i))
 If (strOut &lt;&gt; vbNullString) Then
 strOut = strOut &amp; &quot;, &quot;
 End If
 strOut = strOut &amp; Trim(data(i))
 End If
 Next
 Set col = Nothing
 removeDuplicateWords = strOut
End Function

Public Function existInCollection(ByVal key As String, ByRef col As Object) As Boolean
 existInCollection = existInCollectionByVal(key, col) Or existInCollectionByRef(key, col)
End Function

Private Function existInCollectionByVal(ByVal key As String, ByRef col As Object) As Boolean
On Error GoTo Error
 Dim value As Variant
 
 existInCollectionByVal = True
 value = col(key)
Exit Function
Resume
Error:
 existInCollectionByVal = False
End Function

Private Function existInCollectionByRef(ByVal key As String, ByRef col As Object) As Boolean
On Error GoTo Error
 Dim value As Object

 existInCollectionByRef = True
 Set value = col(key)
Exit Function
Error:
 existInCollectionByRef = False
End Function
</code></pre>
Usage:
<pre><code class="code-1 nolinks" id="code-20-42390443-2">Dim strTest As String

strTest = &quot;world, leader, recognized, entirety, utility, system, system, system, system, Standards, Standards, standards, standard, standards, Automated, portable, national, system&quot;
strTest = removeDuplicateWords(strTest)
Debug.Print strTest
</code></pre>
Side note: It is case insensitive.
</div>

<div>
<div class="content wysiwyg-content">
need to remove all the dupes WITHIN a comma 
 
world, leader, recognized, entirety, utility, system system system system, Standards Standards standards standard standards, Automated, portable, national, system 
 
to 
 
world, leader, recognized, entirety, utility, system, Standards standard , Automated, portable, national, system
</div>
</div>

need to remove all the dupes WITHIN a comma

world, leader, recognized, entirety, utility, system system system system, Standards Standards standards standard standards, Automated, portable, national, system

to

world, leader, recognized, entirety, utility, system, Standards standard , Automated, portable, national, system

remove dupes in a cell

Visual Basic for Applications (VBA) enables building user-defined functions (UDFs), automating processes and accessing Windows API and other low-level functionality through dynamic-link libraries (DLLs). VBA is closely related to Visual Basic and uses the Visual Basic Runtime Library, but it can normally only run code within a host application rather than as a standalone program. It can, however, be used to control one application from another via OLE Automation. VBA is built into most Microsoft Office applications.