The following has been confirmed by the Star-K kashrus organization. There have been reports of real Shatnez in UGG boots and shoes. This is a severe Torah prohibition. Your UGG shoes and/or boots may contain Shatnez and should be checked by an authorized Shatnez expert. See below for a) What needs checking, b) Directory of Shatnez Laboratories. Also, see below for examples where Shatnez has been found in UGG shoes and boots.
Rabbi Yehudah Abrams of DATA does checking here in Dallas. Call 214-987-3282 to reach Rabbi Abrams.
The following was submitted by a shopper, and was confirmed by The Lakewood Scoop with Rabbi Sayagh of the Shatnez Laboratory:
“I recently ordered these Ugg sneakers from Zappos. We noticed a sticker on the bottom that says it contains wool (as seen in pic). I took it to be tested for Shatnez where they found linen fibers in the canvas. The wool couldn’t be removed (even though its only in the inner heel of the shoe) as it was sewn in strongly and he didn’t think all of it could be removed. As these are a popular style shoe, I wanted to let readers know about this Shatnez issue.”
Rabbi Sayagh noted that this is only an issue with the canvas sneaker – the vinyl and leather ones are okay.