Our 5.5 year old Corghi Mix Horrible Skin

I haven't had that experience with any of my dogs.  I do work for a Vet that runs those tests all of the time. They are very pricey but they do eliminate the guessing game.  I think that all the test consists of is taking your dog to the vet and having blood drawn. I believe that the company that the blood is sent to is called VARL although I don't know what it stands for.  After a couple of weeks the company sends  a printout to the vets office.  You would be suprised what kind of things that a dog can be allergic to.  The printout tells you something like what percentage of certain things that your dog is alllergic to.  Normally it's certain weeds or trees.  I even saw one that said that the dog was allergic to cockroaches!

Do you clean with pinesol?  I know a lot of dogs are allergic to that and some other cleaners... they can be allergic to Tide detergent, to some dryer sheets, to some perfumes... etc.  It may help if you get him on some fish oils... the vet I work for sends home skin formula 3v caps to almost every patient who comes in with allergy issues.

Boy that sounds SOOO like atopic allergies.  Dogs can be allergic to everything humans can -- pollen, trees (oak, maple, hay, ANY grass, tons of weeds and plants) -- and sometimes those allergies clear up because they are **seasonal**. 
 
Usually food allergies are what they call 'secondary' .. They are totally real, but may not even show when the environmental things that are the 'primary' problem are low.  So when the seasonal stuff calms down, the food allergies may be the only thing bothering.  This is why they may 'help' when treated but not 'cure'.
 
Try the Benedry LONG term.  They do get used to it.  That takes months -- but they DO.  You have to dose it right and you have to give it continuously for it to do ANY good.  It may diminish the scratching right off -- BUT what a dog breathes in today may not show up on the skin until next week!!  So you have to use it continually to know if it is helping.  Besides -- just keeping the scratching down helps SO much because it keeps them from tearing their skin.
 
The next thing you can try is different types of antihistamine.  Dogs can take lots of different ones.  Diphenhydramine (Benedryl), hydroxyzine (vet prescribed only, not given to humans any more), clemastine (Tavist), and even Claritin (and I can't remember the drug name of that one), and even Chlor-trimeton (chlor...something maleate)
 
But they are ALL dosed **differently** so get your vet's input on that.  Benedryl is cheap and easy -- 1-2 mg/lb body weight (keep the 2 mg dose for tough stuff like bee stings -- start with the 1 mg/lb dose) but give it like 2-3 times a day.  Diphenhydramine only lasts 6 hours in the body -- so twice a day is bare minimum, but you want to give it more frequently those times of the year when the seasonal allergies are worse. You may ultimately be able to guess what it is -- is it worse when the heat in the house is on?  Wall paper dust, dust mites.  When the weather is wet?  mold in an earth cellar, growing leaves, grasses and stuff outside.
 
Frankly I'm not big on knowing exactly what it is -- as long as I can control it and identify it as allergy.  But to each their own.

  Welcome to idog PitOrch;  [] $500 seems over the top for allergy tests; Jessie had the blood test and the skin test and the two together didn't cost that much. There were other expenses such as lab fees for a thyroid panel and cytologys of her feet, ears and other areas of her body as well as a charge for anethesia for the skin test but still three visits to a veterinary dermatologist along with all the tests and the vaccine only added up to about $700. I went to a veterinary teaching hospital; it may be cheaper than a regular vet if you have that option. They even sent the blood to Michigan State University for the thyroid test. Maybe vets charge more where you live but that seems very high.
  Understand that Jessie had suffered with allergies for years and antihistamines didn't seem to help and we tried all of them;  I suggest you use a fatty acid supplement too because that can make the antihistamines more effective. As she got older her symptoms worsened; she had skin infections more frequently; topical treatments that I had used when her skin was irritated didn't work anymore and she ended up at the emergency vet a few times on the weekend because her symptoms were so severe we couldn't wait until our vet opened on Monday. The reason to have the allergy tests done is to formulate a vaccine with the allergens that affect your dog; if you aren't interested in immunotherapy you're probably wasting your money.  It's called allergen immunotherapy. Jessie reacted significantly to over two dozen allergens; they were grass, tree, and weed pollens as well as dust mites and storage mites. The vaccine can't contain more than twelve allergens to be effective; based on the blood and skin tests and Jessie's history the dermatologist determined which allergens to include in the vaccine. Dogs have an allergen threshold ( people do to) and the idea is if they are immune to some of the things they're allergic to it reduces their allergen load below their threshold level and they don't have symptoms. It has been a tremendous help for Jessie; I can remember calling our vet on New Year's Eve because the toes on her right front foot had suddenly swelled for example. Callie's advice is excellent and I recommend you try her suggestions before doing the allergy testing. Besides antihistamines, bathing your dog helps because they absorb allergens through the skin; you can bathe the dog whenever it becomes itchy. Vacuuming  your carpeting, upholstered furniture, and curtains at least once a week reduces the amount of pollens tracked into the house. The best way to protect your dog from allergies to dust mites is to keep him out of the bedroom, wash all the bedding in hot water once a week, or put an allergen matress cover over the matress. Good luck and feel free to ask more questions; Callie knows a lot and so does Cathy (Cakana) and others so maybe you can get the help you need without going through the testing.

My derm vet just told me last week that it would cost $250 for the allergy test using a blood sample.  We didn't discuss the skin testing (yet).  I'm guessing that California is higher than most areas, but I could be wrong. 
 
I'm certainly not an expert, but based on my experience, I'd say the two best things you can do are frequent bathing or even just cool water rinsing, and IF you can find an antihistamine to work, using that as needed.  Sometimes, as in my case, even that doesn't help enough and then you try other things.  I use the Derm Caps or 3V caps, and I think it helps too.  It really is a lot of detective work, and trial and error.  If all else fails and the dog is miserable though, then the money spent on allergy testing is well worth it.  If I had it to do over again (pre- the $$$s I've spent the last 6 months) I'd go for it.  If it turns out there are allergens that you can eliminate, you've got your answer.  If not, many people have had success with the allergy shots.