I'll admit, I was a little skeptical about how well this shirt would work for our 11 year old black lab mix, Mollie. She has ALWAYS been deathly afraid of thunder - when a storm blows up, she paces, pants, trembles uncontrollably, and is just generally very, VERY anxious. We could never provide her much solace, even in our laps. But, I had seen a wonderful movie on HBO called "Temple Grandin" starring Claire Danes in the title role. This true story is about an amazing autistic woman who, through courage, strength of will, and a brilliant mind, completed college and earned Master's & Doctoral degrees in animal sciences. She also is a pioneer in new approaches to cattle ranching and slaughter house management. By empathizing with the animals, and keenly observing their behavior during immunizations, dips, and being lead into the slaughter house, she redesigned much of how it all was done, leading to much calmer & easier to herd cattle, and as humane as possible slaughter.
Anyway, early in the movie, while spending a summer as a teenager at an aunt's cattle ranch for the summer, she observed that the cattle were calmed when placed in a holding device called a "squeeze chute" that pressed in on them tightly. She was fascinated by it, and her aunt allowed her to try it out. Finding that it calmed her nervousness dramatically, she built a smaller-sized version for herself that she used while in college and beyond.
Remembering this from the movie, I decided to get a Thundershirt for Mollie. Well, let me tell you, it works wonders, at least for our Girl. In fact, it is thundering outside as I type this and Mollie, with her pink rugby-style Thundershirt on is laying calmly on the floor in her bed beside me. No panting, trembling or pacing. No apparent anxiety at all! And, to top it off, my wife is vacuuming in the next room (another "trigger" for Mollie's anxiety), and she is apparently not bothered by it either.
Your "mileage may vary" as it is said, but I recommend you at least try one for yourself if you have a dog who gets overly anxious during thunderstorms. If it works half as good as it does for our Mollie, just think how much happier & at peace your dog will be during a storm!
Oh, and as an aside, unlike some other reviewer's dogs, our Mollie has no problem moving around & relaxing when wearing her Thundershirt. The key, I think, is to be sure & order the correct size by measuring your dog around the deepest part of their chest. Doing this caused me to order one size larger than I would have guessed she needed. Also, don't put it on too tightly! Finally, while the material could cause her to be hot, we run the air conditioning in our house consistently at 72° and she is comfortable while wearing it.