You should look at gettext
filter hook which is applied to the translated text by the internationalization functions (__(), _e(), etc.). eg:
add_filter( 'gettext', 'my_sanitizer', 20, 3 );
/**
* my_sanitizer
* @param string $translated_text the translation
* @param string $text the origial text from __()
* @param string $domain text domain
* @return string
*/
function my_sanitizer( $translated_text, $text, $domain ) {
$translated_text = trim(strip_tags($translated_text));
return $translated_text;
}