Boston Terrier Loosing Hair

Question
I have a 16 month old Boston Terrier male (acquired at 8 mos). Neutered in July, 09. Since about 1 week after his surgery, he has been loosing his hair on ear backs, belly and inner thighs. There are no sores and he is not scratching any more than usual (which is normal to less than normal based on other breeds, etc. we've owned). We ALSO got another dog (rescue) in early July (3 weeks before neutering) 16 weeks old. She is a Basenji mix-not a shedder-until recently.
Since the acquisition of the female, both dogs have spent a great deal of time outdoors-they love running, chasing each other, and generally having a good time. BUT for the last 2-3 weeks she is shedding. So I am unsure if it is general "shedding" time for both as the weather is beginning to change, if my Boston has a grass allergy, or if he has Demodex mites. Since my Basenji has begun to shed, when she didn't at all before, I am leaning towards the mites.  The only other symptom my Boston has is very pink skin....but because he has no hair now, that could be the way it looks normally.  Who knows?  I just had to pay for both to be fixed, have doggy checkups/shots, and am pretty much busted $$ for a month.  I have read everything I could find to try and eliminate things.  My Bostons food is the same, our laundry detergent is the same, his shampoo (baby wash) is the same.  The only difference is his time outside (his time has quadrupled since the Basenji arrived as they LOVE it outside now), and the recent surgery (I read that stress from surgery will cause hair loss too).  Can you help me eliminate anything?

Answer
If you suspect mites, either demodex or sarcoptes, they will need treatment.  If your funds are low, have both the dogs dipped with amitraz at the vet for mites.  If it is sarcoptic, they will die from one treatment and you should see improvement.  If not, then it could be demodex and it may require skin scrapings and mulitple amitraz dips.

It could also just be allergies.  Treatment is steroids for that.