From various sources, including the AP:
The FDA issued a statement that adults using prescription testosterone gel should be cautious and avoid its contact with children to avoid causing serious side effects. This week a black box warning was added to several products, AndroGel and Testim.
AndroGel is approved to be applied to the abdomen and shoulders and arms, while Testim can only be applied to the arms and shoulders. An FDA rep. has informed that in a few reports people had applied the product to their chest and then held their children without wearing shirts.
As of December 2008, the agency had received eight cases of secondary exposure to the products in children ranging in age from nine months to five years. Other reports have since come in, the FDA said. In most cases the side effects in children regressed after they weren't exposed to the product, but in a few instances enlarged genitalia didn't fully return to age-appropriate size and bone age remained modestly greater than the child's chronological age. Source here.