FRENCH TERRIER WITH URTICARIAL RASH BAD BREATH & LOOSE STOOLS.
I am a pediatrician with a 18 month French Terrier.
Pink urticarial rash on the underside on/off for 2 weeks. PUTRID breath. Loose stools. Tempted to treat with Adrenaline Benadryl & Prednisone (seems like allergic reaction).
Drinking OK. Acting less active than usual. Shivering/Shuddering at times but no spasticity.
I'm afraid I'm not a veterinarian, and it sounds to me as though your pup needs to be examined by your own veterinarian I'm afraid.
The symptoms you describe could be caused by a number of different things, and allergies are definitely one of them. However, they sound severe, more diverse, and longer lasting than I would expect with an allergy.
A parasitic type infection such as Giardia, Coccidiosis or even Leptospirosis are also possible.
The lethargy, loose stools and shivering indicate that your dog is really feeling unwell, so I'd recommend having your vet run a fecal test and anything else he thinks necessary. That way you'll know for sure what's causing the problem and get the right treatment started.
If you want to give your pup Benadryl to see if it helps relieve the symptoms, I believe the dosage is 1/2mg per pound of body weight, but your vet would be the best person to give you that info. if you need it.
I'm sorry that I couldn't be more help, but I hope you find out what's making your dog so miserable and uncomfortable. Best of luck