- such as those caused by shampoo or body oils
- Bathrooms with poor ventilation
It can appear pink, orange, or yellow. While it is generally harmless to healthy individuals, it’s unsightly and can be a sign of excess moisture.
3. Nicotine or Tobacco Residue
If anyone smokes—or used to smoke—in the home, nicotine residue can:
- Accumulate on walls over time
- Turn yellow when exposed to humidity
- Drip down when moisture condenses on the walls
