How to Delete Your Search History on Facebook App (Android/iOS)
First of all open Facebook on your phone.
Now tap on the search icon that appears on the screen.
After the search opens, tap on Edit.
Now, your activity log will open, and you will need to tap ‘Clear Search’ to clear your search history on Facebook.
how to delete your search history on facebook web
First of all open www.facebook.com in your browser.
Click the drop-down arrow in the top right corner of the screen, select ‘Privacy and Security’ and then click ‘Activity Log’.
Select ‘Logged action and other activity’ in the Activity log.
Now select ‘Search History’, then click ‘Clear Search History’.