SKIN/EAR PROBLEMS - LABRADOR

Question
Our 10 month old labrador scratches a lot - chews his bottom, ears, rump, neck, around mouth and eyes.  Frequent gummy eyes in morning.  Has his anal glands regularly checked and periodically expressed so the vet doesn't think that's what's causing his bottom chewing.  No signs of any skin lesions.  Is on regular Revolution, wears a tick collar, regularly wormed.  The vet suspects he might have an allergy so he is now on a special allergen-free diet (started 5 days ago) and scrapes have been taken (all negative).

The pressing problem however is his right ear which is smelly, black discharge and very sore.  Shakes his head, yawning and has a good scratch several times an hour. We've been given Epi-Optic to clean it and Framoptic drops to put in, but he won't let me near his ears!  Loves having them rubbed, but the minute he sees the bottles will not let me touch him.  The vet has been unable to examine his ear because of this so the treatment is a best guess.   

We live in Hong Kong. He is a rescue dog so we have no idea of his background.  Otherwise he is a delightful, obedient, loving, healthy dog.  We have another dog (mongrel, approx 11 months) who is also itching but nothing like the lab.  Awaiting fungal culture results (from both of them) from the vet.

On Saturday we go on a 2 week holiday and I don't want to leave him with such a bad ear and with no chance of getting the medication in.  Can I get some oral treatment instead?  Or should I request for him to be sedated for the vet to get a proper look in his ear?  
Thanks very much for your time.  

Answer
I would definitely have him sedated so the vet can get a look and a sample of the goo in the ear for analysis. That way, specific treatment can be offered.

The diet is a good idea and it needs to be done for at least 2 months before stopping it. Do not give any other food or treat by mouth.  

As far as what else can be done, I would ask the vet to give a shot of a steroid called dexamethasone to try and relieve the swelling and pain in the ear. That will also tell you if it is an environmental allergy.