The other day I happened to be in a grocery chain owned by a Japanese family and was surprised and delighted to see Yakult (Esperanto for yogurt – not a Japanese word!). It is the only commercial source for Lactobacillus casei Shirota. It is available at some US locations, click here to search. There are two chains in Seattle area that carries it.
- A study failed to find clear evidence of any clinical impact on hay fever, while an early one did 
I came home and because it was known to reduce mast cells release of histamine, and my wife was miserable with hay fever, she agreed to try some. To everyone surprise, her hay fever disappeared within 20 minutes and stayed away for over 18 hours. There was a side effect, a bit of diarrhea (which may have been cause by the high sugar content). In an earlier post, this species and Bifidobacterium lactis NCC2818 were well documented as effective for treatment.Some are known to have no effect such as E.Coli Nissle 1917 . Some authors feels that some general families are to be avoided for example “Lactobacillus casei,and Lactobacillus bulgaricus.”[source] [source], however if you can get an actual strain that is know to be good then use it (for example: Shirota cited above) A year ago, I posted about what increase histamine and decreases histamine, note that the L.Casei family in general increase histamine, but the shirota stain does the opposite effect (just like Mutafor (E.Coli Nissle 1917) is a good E.Coli.
- No Impact
Bottom line, there is only two that appear to be “easily” available:
- Lactobacillus rhamnosus (L. rhamnosus) GG (LGG(®)  aka Culturelle
- Lactobacillus casei Shirota aka Yakult
My wife had been taking Culturelle, so IMHO, for her at least, Yakult is far more effective.
http://www.actimel.com/ is Danone “mimic” of Yakult and appears to have similar characteristics. It’s available in most of Europe and Canada