Memory foam consists mainly of polyurethane as well as additional chemicals increasing its viscosity and density. It is often referred to as viscoelastic polyurethane foam, or low-resilience polyurethane foam. The foam bubbles or cells are open, effectively creating a matrix through which air can move. Higher-density memory foam softens in reaction to body heat, allowing it to mold to a warm body in a few minutes. Newer foams may recover their original shape more quickly.
Memory foam was subsequently used in medical settings. For example, it was commonly used in cases where the patient was required to lie immobile in their bed on a firm mattress for an unhealthy period of time. The pressure on some of their body regions impaired the blood flow to the region, causing pressure scores or gangrene. Memory foam mattresses significantly decreased such events.