Why is there black residue on the aluminium, refillable deodorant case?Updated 11 days ago

The residue you’re seeing is a fine layer of aluminium oxidation, which is completely normal. This tends to occur on the threads or moving parts of aluminium packaging, particularly in areas that are uncoated, unpainted, or subject to regular friction.

If you happen to get the residue on your skin, please note that these stable particles are too large to be absorbed by the skin and stay safely on the surface.

A quick wipe around the threads of the aluminium case and lid from time to time with a soft cloth or paper towel should help manage this easily.