How long does a 5L hand wash last?
For most households, many months and a great many bottles' worth. It is the most economical way to buy it.
When should I apply hand lotion?
While hands are still slightly damp after washing. It works noticeably better than applying to fully dry skin.
Which is best for sensitive hands?
The fragrance free versions, since fragrance is the usual culprit. Drying hands properly helps as much as changing product.
Can I refill my existing pump bottle?
Yes, and that is rather the point of the 5L. The pumps last for years.