Many detergents (even shampoo and bath foam) add in Sodium Lauryl Sulphate (SLS) to artificially create foams, to give the impression of a clean wash. But these foaming agents / chemicals are very dry to the skin.
I used Pigeon Liquid Cleanser to clean bottles. Milk contains fats, so wash the bottles / teats in WARM soapy water to get rid of the oily residue. Just use the recommended amount stated on the bottle. If used too much, might not wash away thoroughly.