For iguanas, the uv is their source of vitamin D3. Well, that being the case, then the drops are pointless for them. It is believed that iguanas can not absorb D3 from their food and require the lighting to obtain it. Without the d3, they can't properly assimilate dietary calcium and phosphorus. that would lead to problems like MBD. I think that product is just another gimmick for the distributers to grab a buck off the unknowing newbie!