Food Safety News performed a series of lab tests at Texas A&M University to learn if the labeling on honey sold in major stores was reliable. Why is this important? Because "ultra filtered" honey, which sounds more pure, actually isn't:

Ultra filtering is a high-tech procedure where honey is heated, sometimes watered down and then forced at high pressure through extremely small filters to remove pollen, which is the only foolproof sign identifying the source of the honey. It is a spin-off of a technique refined by the Chinese, who have illegally dumped tons of their honey - some containing illegal antibiotics - on the U.S. market for years.

Hiding the pollen in honey is a technique to prevent tracking of its source of production, and thus to disguise its impurity, not its purity.

What were the results? Not good:

• 76 percent of samples bought at groceries had all the pollen removed. These were stores like TOP Food, Safeway, Giant Eagle, QFC, Kroger, Metro Market, Harris Teeter, A&P, Stop & Shop and King Soopers.
• 100 percent of the honey sampled from drugstores like Walgreens, Rite-Aid and CVS Pharmacy had no pollen.
• 77 percent of the honey sampled from big box stores like Costco, Sam's Club, Walmart, Target and H-E-B had the pollen filtered out.
• 100 percent of the honey packaged in the small individual service portions from Smucker, McDonald's and KFC had the pollen removed.

The best defense appears to be to purchase honey labeled as "organic", which seems to usually come from Brazil.

Much more detailed information, including brand names, is here.