Nonionic surfactants are surface active agents which do not dissociate into ions in aqueous solutions, unlike anionic surfactants which have a negative charge and cationic surfactants which have a positive charge in aqueous solution. Nonionic surfactants are more widely used as detergents than ionic surfactants because anionic surfactants are insoluble in many hard water and cationic surfactants are considered to be poor cleaners.

In addition to detergency, nonionic surfactants show excellent solvency, low foam properties and chemical stability. It is thought that nonionic surfactants are mild on the skin even at high loadings and long-term exposure. The hydrophilic group of nonionic surfactants is a polymerized alkene oxide (water soluble polyether with 10 to 100 units length typically). They are prepared by polymerization of ethylene oxide, propylene oxide, and butylene oxide in the same molecule.

Depending on the ratio and order of oxide addition, together with the number of carbon atoms which vary the chemical and physical properties, nonionic surfactant is used as a wetting agent, a detergent, or an emulsifier. 

HLB (Hydrophilic-Lipophilic Balance) values for proper applications.
<10 : Lipid soluble (or water-insoluble)
>10 : Water Soluble
4-8 : Antifoaming
7-11 : Water-in-oil emulsion
12-16 : Oil-in-water emulsion
11-14 : Good Wetting
12-15 : Good detergency
16-20 : Stabilizing

Nonionic surfactants include alcohol ethoxylates, alkylphenol ethoxylates, phenol ethoxylates, amide ethoxylates, glyceride ethoxylates (soya bean oil and caster oil ethoxylates), fatty acid ethoxylates, and fatty amine ethoxylates. Another commercially significant nonionic surfactants are the alkyl glycosides in which the hydrophilic groups are sugars (polysaccharides).