Baby chick with bald and swollen backside?! HELP!

[arianebrust]

So I got some chicks yesterday and there's one with a very swollen and bald butt! I don't know what this is or how I could treat it. They're only about 6-8 weeks old so I know that it's not an egg. If anyone could help me out I'd appreciate it!

Thanks!

 

[RAWR]

put some vic-sab or how ever u spell it on his butt
always works for mine

 

[arianebrust]

I tried typing that in to see what it is and I couldn't find anything... Is there any way to find out what the name of it is?