Parents and caregivers, of children 2 years-old and younger, are being warned that teething gels and creams (that contain Benzocaine) can cause rare, but potentially deadly, side effects on those children. That’s because Benzocaine can cause a rare blood condition that has been linked to breathing problems. Symptoms can include shortness of breath, headache, and rapid heart rate. Although there are similar over-the-counter products for adults (with toothaches and cold sores), Benzocaine is not considered to be dangerous for adults.