First the good news; since clearing the dust from my house, his underbelly and underarm skin redness has largely disappeared and his fur has grown back in those areas. The ear pinnae have returned to a lighter shade as well, except when he scratches them.
He was vomiting or regurgitating a thick foamy liquid overnight. We tried the stomach emptying drug Cisapride, but he violently vomited 3 times on the third day of taking this after his late afternoon meal which is unknown for him, so we stopped this immediately. This is the third type of medicine he has adversely reacted to, the others being Cytopoint and Apoquole. I wondered if the empty stomach might be exacerbating the issue, so I started to feed him around a third of his food last thing at night in an attempt to keep it full. He hasn't vomited since, despite withdrawing Omprazole and antacids.
My big worry though is the continuing lip licking & swallowing and the atrocious smell from the mouth which accompanies this, which suggests he is continuing to regurgitate. Both of the vets I've asked to examine him, think Megaoesophagus unlikely, because he eats well, he doesn't react to pressure on any part of his body, and is still active. However, he's dropped from a slightly overweight 40kg to 30kg over the last year, and I'm starting to feel his ribs on examination.
He also continues to be bothered by his ears as indicated by vigorous head shaking, despite me (trying to) apply ear cleaner every morning. I intend to take him to the vet for another ear clean soon. The last time they were cleaned one ear was blocked by what I think was green ear wax, whilst at other times the wax was black but more scattered. I will ask the vet to take a sample to determine the fungi/bacteria balance, and note the amount of wax being produced. Is the type of fungus important (I live next to a swamp and have suffered fungal ear infection myself). I'll also ask them to check his lips for pyoderma and take blood samples for testing whilst he's sedated, these can be compared with some taken 21 months years ago when all this started, then there were mostly OK, but two borderline readings which could be explained by atopic dermatitis.
Regarding the type of food, I recently tried a high protein diet: raw chicken dog food, eggs & some low starch veg to starve any potential endemic fungus. It was a disaster, all his symptoms soared. He was gurgling when sleeping, and the skin inflammation returned. So Chicken or egg is another confirmed allergen! So far I've tried insect protein, Hydrolyzed Chappie (which contains a small amount of chicken), and food with probiotics, none of which prevents the smell from his mouth and frequent ear blockages. I'm running out of options on what to try, I'm currently giving him a diet of fish without grain. I suppose insect protein + root vegetables would guarantee no food allergy?
The only medicines he's taking at present are Nexguard and Droncit. In view of his reaction to all the other drugs, is it worth changing these, or even stopping them over the winter period? I may have changed to these drugs from other anti-parasitics within a year he started to have his gastric problems, but I'll have to check the date of this change. He certainly doesn't become any worse on the days following taking these drugs on a monthly and three monthly rota. Note he had quite bad atopic dermatitis for 3 years prior to this without any smell from the mouth or gastric problems.