Surfactants can make up as much as 50 percent of the shower gel content, with the remaining proportion being made up of a combination of water and ingredients to thicken, preserve, emulsify, add fragrance, and color. Multiple surfactants are often used to achieve desired product qualities. A primary surfactant can provide good foaming ability and cleaning effectiveness, while a secondary surfactant can add qualities of mildness to prevent irritation or over-drying of the skin. To prevent shower gel ingredients from separating, emulsifiers such as diethanolamine are added. Conditioning agents may also be added to moisturize the skin during and after product use. They are also available in different colours and scents. Ingredients, like scent in the form of essential oils or fragrance oils and colorant in the form of water soluble dyes are common in shower gels.