Why? Well, let's take a look at the following conversion. So, if there's a build up of galactose inside our body well, first of all, this is a cyclical galactose and this is its open chain confirmation. And so if there's a build up of the galactose, an enzyme known as Aldos reductase will use this molecule and the H plus ion to transform this sugar molecule into an alcohol known as galactitol. Now, galactitol, if there's a build up of galactitol in certain areas of our body, that can cause very, very dangerous conditions. So the high concentration of galactose and subsequent high concentrations of the alcohol, galactitol is toxic to the body and it can actually cause damage to many areas of our body.