function getSelectvalues(select) {
  var result = [];
  var options = select && select.options;
  var opt;

  for (var i=0,iLen=options.length; i<iLen; i++) {
    opt = options[i];

    if (opt.selected) {
      result.push(opt.value || opt.text);
    }
  }
    //alert(result);

  return result;
  }

 <div id="DROPDOWN"  onmouseout="getSelectvalues(this)">
       <select onmouseout="cancelBubble();"  onchange="getSelectvalues(this)"   data-style=""    
      class="selectpicker form-control"  id="multipleSelected" multiple="multiple">
      <apex:repeat value="{!MedicalAllergies}" var="itm">                                                   
      <option  value="{!itm.label}">{!itm.label} </option>
      </apex:repeat>
      </select> 
</div>