Emulsion-type ointment includes water-in-oil emulsifier and water-in-oil emulsifier. Oil-in-water emulsions, also known as creams, have the advantages of fast release, easy absorption by the skin and no greasy feeling. However, in oil-in-water formulation, direct contact of water with the skin is easy to evaporate, the skin will be drier after evaporation, and the moisturizing time is relatively short. Oil-in-water emulsion is suitable for oily skin diseases, such as acne, seborrheic dermatitis and acute eczema. Drugs in oil-in-water emulsions, in order to play a role, need to first diffuse from the water phase to the surrounding oil phase, and then from the oil phase to the skin surface, so the release rate is slower, with long-term function, moisturizing effect will be stronger. Oil-in-water emulsion is suitable for chronic eczema and skin damage requiring more lasting moisturization.

In the ointment, the ointment which is easy to be coated and made of emulsion matrix is called the ointment. External cream can improve the permeability of skin and mucosa and reduce irritation. Allantoin cream is a kind of cream. The preparation process of the cream is complex, and the oil and water phases need to be prepared separately. Drugs enter one phase according to their solubility. These two incompatible liquids, through emulsification and other steps, a liquid dispersed in the form of droplets in another liquid, forming a heterogeneous liquid preparation, after condensation into a paste, is a cream.

Allantoin has strong moisturizing effect and is also a keratin promoter. It can increase the hygroscopicity of skin keratinocyte adhesives. It can also directly act on keratin molecules, promote their ability to combine water, absorb more water, and moisturize the skin. At the same time, allantoin can disperse keratin, dissociate scales, shed, and make skin smooth and soft. The keratinolysis and cleansing activity of 0.2% allantoin is equivalent to that of 10-20% urea, but there is no irritation of urea. Allantoin has both local anesthesia effect and can alleviate the irritant and relieve itching. It can also stimulate epithelial proliferation, promote the growth of granulation tissue and promote wound healing. Because of these advantages, allantoin is widely used in cosmetic cream, lotion and essence.