Substances that can cause numbness in the fingertips on contact are liquid nitrogen and dry ice, which is frozen carbon dioxide, according to About.com and the University of Vermont. Touching these substances leads to frostbite, one of whose symptoms is numbness, according to Mayo Clinic.
Continued contact with these substances leads to discolored skin and skin that has a waxy look, says Mayo Clinic. In severe cases, the skin forms blisters after it is rewarmed. Experts stress that both liquid nitrogen and dry ice only be handled if the handler is wearing thermal gloves.
Liquid nitrogen is a by-product of the distillation of liquid air, explains About.com. It is a bit lighter than air and boils at -320.4 degrees Fahrenheit. It is odorless, colorless and non-toxic. Though liquid nitrogen is not flammable, oxygen can accumulate in containers that hold liquid nitrogen. As the liquid nitrogen boils away, the oxygen can combust when it comes into contact organic matter.
At temperatures above -109.3 degrees F, dry ice turns directly from a solid into a gas, says the University of Vermont. Though it is not flammable, dry ice can explode if a large amount of it is stored in an unventilated container. It can also be a suffocation hazard if a lot of it is kept in an unventilated room.