Dr. Manny walked into the office this morning huffing and puffing about something new that was bothering him, so against my better judgment, I asked him about it.

He pointed to his wrist and said, “See these cute little bracelets? They’re called Silly Bandz, and I think they could potentially be harmful to children if they’re not careful.”

At first glance, these bracelets called “Silly Bandz,” are very cute. They come in all different shapes, like foods, letters and animals—and kids are becoming obsessed. At just five dollars for a pack of 24, they are rushing out after school to buy them. Stores can hardly keep the rubber bracelets on their shelves. Kids trade them and try to out-do each other by seeing who can collect the most. In fact, it seems the more a child wears, the higher their social status on the playground.

Last night Dr. Manny’s young daughter had more than a hundred of these Silly Bandz wound tightly around her wrist. Her hand was white, and he was concerned enough to make her take them off.

It reminded him of the way kids collected baseball cards when he was growing up — but those were kept in a box under the bed. “Silly Bandz on the other hand, may be a health hazard that could potentially cause a constriction of blood flow to the hand,” Dr. Manny said.

So, wondering if this could really be a problem, I decided to ask a vascular surgeon: If a child keeps these bracelets on for hours at a time, could it cause a serious health problem?

Dr. Gregory Simonian, chief of endovascular surgery and director of the Heart Vascular Hospital at Hackensack University Medical Center, told me that his daughter also wears Silly Bandz, and that Dr. Manny could be on to something.

“Whether it’s tight bracelets or a ring on your finger, anything that is constricting could cause vascular insufficiency—meaning the blood flow is being altered by some external force. In this case, it’s the new, hip rubber bracelets,” Simonian said.

Veins leaving the hand are low pressure, so it wouldn’t take much, especially on a child, to constrict the flow.

“These bands could cause what we call a tourniquet effect that can cause your veins to get congested. The bracelets could cause blood clots to form in some of the veins, giving someone a phlebitis, which is an inflammation and clotting of the vein,” he said.

Dr. Manny was especially concerned for kids who wear numerous Silly Bandz for hours at a time, or even fall asleep at night with them on.

“If left on for a really long time, and the bands were tight enough, it could begin to compromise the arterial blood supply going into the limb, but that would be extreme and very unlikely with these little rubber bracelets,” Simonian said.

When contacted for a statement on the safety of the product, a representative from Silly Bandz said there is a warning label on the back of our packages right next to the UPC code. It says it contains choking hazards, small parts, and is not suitable for children under 3 years of age.

Simonian told me that wearing a few rubber bracelets will more than likely be nothing to worry about, but there are symptoms parents can watch for if their child has many of them on his or her wrist.

“If the bracelet is causing a significant indentation in the skin and the tissue, causing arm swelling, a change in feeling like numbness or tingling, or color change, those are all signs that the bands are constricting and need to be cut off immediately,” he said.

Looks like Dr. Manny was right.