When you get a allowed memory size exhausted error you need to increase your php memory_limit value. If you’re allowed to edit the PHP.ini file, update your memory_limit in PHP.ini by modifying the below line:
memory_limit = 256M;
If you can not access the php.ini file, try adding the following to your .htaccess file:
php_value memory_limit 256M
OR, if this also does not work, edit wp-config.php file and add the following before the comment thats all Happy Blogging.