Probiotics are a hot area of scientific research and a booming business in the food world. Experts believe that for most people, foods with probiotics are safe, but more study is needed to determine how much they help.

Q: What are probiotics?

A: They are so-called "friendly bacteria" similar to those living in the human gut.

Q: What do they do?

A: There is emerging lab evidence that in huge amounts, some types of these bacteria can help prevent or treat some digestive problems, diarrhea and allergic skin reactions. Scientists around the globe are studying other potential benefits.

Q: What about commercial foods containing probiotics?

A: Experts say they're generally safe and some may even be beneficial, although many haven't been put through rigorous scientific testing. People with weakened immune systems or underlying chronic disease should consult their doctors before trying these products.

Q: What products contain probiotics?

A: Recently introduced probiotic products include specialty yogurts, cheeses, snack bars, cereal, baby formula and supplement pills.

Q: Are all probiotic products the same?

A: Look for brands that contain live bacteria, and that list the amount and type of bacteria they contain. Amounts generally higher than 1 billion per serving are preferable. Lactobacillus and Bifidobacterium are among bacteria shown in some studies to be beneficial.

Q: What about prebiotics?

A: Prebiotics include fiber and other nutrients that feed probiotic bacteria.