Spectrox toxaemia

Spectrox toxaemia was a deadly illness brought on by coming into contact with unrefined spectrox, a life-extending substance found on the planet Androzani Minor. Spectrox toxaemia would first cause blistering and itchiness around the contact area. It would then cause cramps and spasms spreading outwards from the area. Later, there was slow paralysis of the spinal nerve, hallucinations, weakness, and finally death.

This process would generally take a few days. Even the generally robust Time Lord physiology would succumb. The only known cure was the milk from a Queen Bat, a species native to Androzani Minor. The cure was discovered by Professor Jackij.

Peri Brown and the Fifth Doctor both became infected. The Doctor cured Peri with milk from the queen bat but was forced to regenerate to save himself. (DW: The Caves of Androzani)