To that end, it's more than just aluminium that proponents of natural deodorant are seeking to avoid. "Propylene glycol is an additive used to help keep substances, like deodorant paste, from drying out, but if sufficient quantities are absorbed, it has been linked to liver and kidney damage," Dr. King says. " Some studies have linked triclosan to a number of different health problems, including disruption of the endocrine system and increased risk of cancer. Parabens mimic the effects of oestrogen in our bodies, so concerns have been raised about the possible hormonal effects of absorption." She continues: "Then, of course, aluminium has been linked to both breast cancer and Alzheimer's disease — and while there's no empirical scientific data to support the legitimacy of either claim, these concerns are something that people are aware of."