The word “probiotic” which means “for life”, should indicate that a product contains live bacteria and has been shown to have health benefits. Unfortunately, that’s not always the case. Here are some ways to avoid being scammed:
Look for the full name of the probiotic, including the exact strain of the bacteria, because the side effects can be strain-specific. Probiotics are described by three words; their genus (e.g., Lactobacillus), their species (rhamnosus) and their strain, which can be numbers and/or letters (GG). Reputable brands will tell you the exact strain.

Look for quantity of live organisms in a daily serving. Five billion is great. Less than one billion is bad, with some exceptions: Lactobacillus reuteri, which has less than one billion live organisms per daily serving, has been shown to successfully reduce colic in infants.
Look for a seal from the National Yogurt Association (NYA) to make sure the product has “live and active” cultures. Avoid yogurts that say, “made with active cultures.” It might be heat treated after fermentation, meaning the bacteria is dead. (Products such as yogurt-covered pretzels do not contain probiotics.)

For more information you can get the book: The Probiotic Revolution by Gary Huffnagle