Chicken with sore on neck

Question
Hi Abi... We are relatively new to the chicken scene.  We have been raising chickens for just a year now.  I think we have the basics down, but we are still learning.  For instance, we discovered this evening that one of our young hens, an Araucana mix, about four months old, has an open sore on her neck.  It is about the size of a thumbnail, gray, with black around the edges, oozing & stinky.  She seems to be behaving normally, despite this sore.  I am worried about her, but I need to know if this is cause for alarm with regard to the rest of the flock.  My daughter says it looks like another chicken pecked at her.  So could it be an injury that simply got infected?  We have about 25 chickens total, they live in a shed and are let out daily into a fenced yard.  The yard used to be covered in grass, but you know how chickens are with grass, so now it is all dirt.  I have separated her from the flock.  I read in one of your other posts that a salt solution should be used to clean the area and then a course of antibiotics may be needed?  Is there a special way to mix this solution, or do I simply mix salt & water together?  Whatever advice you can offer would be much appreciated.  Thank you for your time.

Answer
Hello Heather,

I think you have answered your own question here! Yes, it will need cleaning with a salt water solution and she will need antibiotics. Just mix as much salt in boiling water (cooled before applied, obviously!) as will dissolve.
As it is on her neck it would worry me a little that she has been scratching at it due to mites- you need to treat your coop and your flock for this as she may have rubbed herself raw.
Also, as it is quite obviously infected you will need to get antibiotics from your vets to stop it from spreading. It is also worth checking over all your other chickens to make sure they are all as healthy as possible.

Thanks for your question, and for taking the time to look through my past answers- it helps me no end when people do this! :)