避免重定向循环服务器端

Question

I have a website that offers the user to enter redirects. Kind of a traditional url-shortener.

Do avoid loops I check if my own domain is entered and don't allow that.

But anyone could use another shortener to do something like that:

http://urlshortener1.com/dbddhkp -> http://urlshortener2.com/dbddhkp
http://urlshortener2.com/dbddhkp -> http://urlshortener1.com/dbddhkp

Or use three, four shorteners

Is there any way to avoid this using pure Server-Code (no cookies) and/or .htaccess-rules without maintaining a long list of available url-shorteners?