Swollen neck and lower jaw on Border Collie/Australian Shepard mix

[Bentleysmom71]

My dog had sudden swelling of his neck and lower jaw.  He is scratching a lot so we gave him a Benadryl inside a treat.  This hasn't helped much, if any and the swelling is not getting better.  I don't think he's eaten much and only drank a small amount.  We are calling the vet at 7 in the morning when the vet opens and am hoping to get in right away.  
Does anyone know why this could have happened?  We do live out in the country and perhaps it's a bite...  I'm preparing for the worst, but hoping for the best. Any advice?

[Bentleysmom71]

Thank you, he is better now,  he had  large abscess under his chin.  The vet drained this and washed it and now he's on antibiotics and more Benadryl for 10 days and then in for a check up and shots updated.  It was a very scary Sunday night, as he was not doing well.  By yesterday afternoon he seemed more like himself, although the Benedryl sure does make him woozy, they told us to give him 2 in the morning and 2 at night.  I think its drying him up maybe too much, now he rubs his snout in the grass all the time and shakes his head slightly.  Thanks for your helpful and kind response!

[skydnsr]

Sorry you didn't get a response sooner.  I hope he's better now.  Was it a bite?  Because that's all I can think of.  It could have been anything from a wasp sting to a snakebite.  Benadryl was a good thing to give as first aid in that situation, and the only thing I can add is to make sure you give enough.  You can give one to two milligrams of Benadryl per pound of dog.  In an acute situation like that, I would give two milligrams per pound, especially if he has taken Benadryl without incident in the past.  Again, I hope everything is resolved and he is doing well now.