https://www.fbrell.com/fb.ui/apprequests
this code removes all requests your app sent to the current user(put it in your default page)
this is not best but because i'm not familiar with your coding this is all i did
this code only works if user installed your app
<div id="fb-root"></div>
<script>
window.fbAsyncInit = function() {
// init the FB JS SDK
FB.init({
appId : 'YOUR_APP_ID', // App ID from the app dashboard
channelUrl : '//WWW.YOUR_DOMAIN.COM/channel.html', // Channel file for x-domain comms
status : true, // Check Facebook Login status
xfbml : true // Look for social plugins on the page
});
// Additional initialization code such as adding Event Listeners goes here
};
// Load the SDK asynchronously
(function(d, s, id){
var js, fjs = d.getElementsByTagName(s)[0];
if (d.getElementById(id)) {return;}
js = d.createElement(s); js.id = id;
js.src = "//connect.facebook.net/en_US/all.js";
fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));
</script>
<script>
FB.api('/me/apprequests', function(response) {
var ids = [];
for (var i=0, l=response.data.length; i<l; i++) {
FB.api('/' + response.data[i].id, 'DELETE', Log.info.bind('clear requests'));
}
});
<script>