Using sunlight (ultraviolet light) for stain removal and sanitisation

Using the sun has been a popular method of stain removal for nappies, and many believe that the sun sanitises. However, if the sun was a completely effective sanitisation method, bacteria on the surface of the earth wouldn’t exist.

Using sunlight to treat stains is not effective

Ultraviolet light (UV) only affects the surface layer of fabric. Nappy inserts are typically multi-layered so UV won’t reach the layers underneath. As a result, any stain removal effect from the sun is effective at the surface layer only. Using UV to remove the stain is it’s only temporary, after storage, it will reappear.

Sometimes these stains are soiling (poo) that has not been washed out. However, stains do not necessarily mean soiling (poo) hasn’t been removed, some foods simply stain (for example, blueberries, carrot, and tomato). Exclusively breastfed poo can also stain.

With enough of a decent detergent, adequate agitation, and if needed a laundry booster, stains will be removed by the washing machine.

Two cloth nappy inserts side-by-side, one with a stain, one without
Staining from exclusively breastfed poo, which was effectively removed with the addition of a laundry booster to the wash cycle

For methods to ensure your laundry comes out of the machine stain-free, see the Wash Routine Basics, and Why Am I Getting Stains pages. Now you can wear those white clothes, and dress your children in those white clothes in confidence!

Using sunlight to sanitise is not effective

UV from the sun is UVA, UVB and UVC wavelengths. When UV light is used to sanitise, in a method called Ultraviolet Germicidal Irradiation, UVC wavelengths are used.1 The majority of UVC is blocked by ozone in the Earth’s atmosphere2 (as a side note, this is also why sunscreens contain only UVA and UVB filters).

The lack of UVC at ground level, along with the multi-layered nature of nappy inserts, means the sun is not an effective method of sanitisation for cloth nappies.

The two most effective, economical and readily available options for sanitisation are chlorine bleach or 90/95°C sanitise cycle.

References and further reading

  1. Wikipedia, Ultraviolet germicidal irradiation <>.
  2. Ciara McCarthy, Slate, Is Sunlight Actually the Best Disinfectant? <>.