Silly Putty is not toxic in the way most parents worry about. It’s made from silicone oil and boric acid, both of which are low-risk in the small amounts present in the product. A child who touches, stretches, or briefly mouths Silly Putty is unlikely to experience any harm. That said, swallowing a large piece or playing with off-brand putties that contain higher chemical concentrations introduces real, if still modest, risks worth understanding.
What Silly Putty Is Made Of
Silly Putty is a silicone-based polymer. The two main ingredients are silicone oil (polydimethylsiloxane) and boric acid, which are linked together using sodium borate as a cross-linker. This combination gives the putty its signature stretch-and-bounce behavior. Silicone oil is biologically inert, meaning your body doesn’t absorb or react to it in any significant way. It’s the same family of silicone used in medical devices, cookware, and cosmetics.
Boric acid is the ingredient that raises the most questions. In high doses, boric acid can cause nausea, vomiting, and diarrhea. At very high exposures over time, it has been linked to reproductive harm in animal studies. But the concentration in a standard egg of Silly Putty is far below levels that would cause these effects. Toxicologists have established that the concerning threshold for boric acid in children starts around 300 milligrams per kilogram of body weight, and a small container of Silly Putty doesn’t come close to delivering that amount even if a child ate the whole thing.
The Real Risk: Swallowing It
The bigger concern with swallowing Silly Putty isn’t chemical poisoning. It’s a physical one. Silly Putty doesn’t break down in stomach acid the way food does. A small piece will typically pass through the digestive tract without incident. A larger piece, though, could potentially cause a blockage, especially in very young children with narrower intestines. Signs of a blockage include persistent vomiting, abdominal pain, and not passing stool.
If your child swallows a small amount and seems fine, watch for those symptoms over the next day or two. If they swallowed a large chunk or show any distress, that warrants a call to poison control or a trip to urgent care.
Skin and Eye Contact
Silly Putty is designed to be handled extensively, and normal play rarely causes skin irritation. Some children with very sensitive skin or eczema may notice mild redness after prolonged contact, but this is uncommon. Washing hands with soap and water after play is enough.
Eye contact is more of a concern, not because of toxicity but because of irritation. If Silly Putty or any residue gets into a child’s eye, flush the eye with clean, lukewarm water for at least 20 minutes. For young children, having them lie back in the bathtub while you pour a gentle stream of water over the affected eye works well. Don’t rub the eye, and don’t use eye drops unless directed by a medical professional. If irritation persists after thorough rinsing, have the eye evaluated.
Off-Brand Putties Can Be Different
While classic Silly Putty (made by Crayola) has a well-established safety profile, not all putties and slimes on the market meet the same standards. This is where the real toxicity concerns come in. In 2018, a UK consumer group investigation found that many slime and putty products sold online and in stores contained boron levels well above safety limits. Several products from various brands were pulled from shelves.
One notable case involved two varieties of Crazy Aaron’s Thinking Putty that were recalled after testing revealed boron levels of 1,797 and 2,062 milligrams per kilogram. The EU safety limit for putties is 1,200 mg/kg, and for slimes it’s 300 mg/kg. Boron at those elevated levels can cause digestive symptoms if a child mouths the product or doesn’t wash hands before eating.
If you’re buying putty or slime from lesser-known brands, especially from online marketplaces, there’s less guarantee that boron levels fall within safe ranges. Sticking with established brands that comply with toy safety regulations (ASTM F963 in the U.S., EN 71 in Europe) reduces this risk significantly.
Homemade Putty and Slime
DIY putty recipes often call for borax (sodium borate), white glue, and water. The risk here is that children or parents may use too much borax, creating a product with higher boron concentrations than commercial versions undergo testing for. Borax in its powder form can also irritate skin more readily than the bound form found in finished Silly Putty, where the boric acid is chemically cross-linked into the polymer.
If you’re making putty at home, use borax sparingly and supervise the mixing process. Children with cuts or broken skin on their hands should avoid handling borax powder directly. Once the putty is fully formed and the borax is incorporated, the risk drops considerably.
What About Repeated, Long-Term Play?
For children who play with Silly Putty regularly, there’s no evidence that normal handling poses a cumulative risk. The silicone polymer doesn’t off-gas harmful fumes at room temperature, and skin absorption of boron from a finished putty product is minimal. The product has been on the market since 1950 with no pattern of chronic health effects reported.
The practical precautions are simple: don’t let very young children put it in their mouths, wash hands after play (especially before eating), and replace putty that has picked up significant dirt or debris. Silly Putty that’s been on the floor collecting lint and pet hair is more of a hygiene issue than a toxicity one.