Agar is a gelatinous substance obtained from the cell walls of red algae, primarily from members of the Gelidiacae, Sphaerococcaceae and Rhodophyceae seaweed families. Commercially it may be prepared from Gelidium amansii. It can be used as a vegetarian gelatin substitute, a thickener for soups and jellies, and as a clarifying agent in brewing. None known side effects in the concentrations used. High concentrations bring about flatulence and bloating.

Agar-agar is a natural vegetable gelatin counterpart. White and semi-translucent, it is sold in packages as washed and dried strips or in powdered form. It can be used to make jellies, puddings, and custards. For making jelly, it is boiled in water until the solids dissolve. Sweetener, flavouring, colouring, fruit or vegetables are then added and the liquid is poured into molds to be served as desserts and vegetable aspics, or incorporated with other desserts, such as a jelly layer in a cake.

Agar is used:

• As an impression material in dentistry.
• As a medium to precisely orient the tissue specimen and secure it by agar pre-embedding (especially useful for small endoscopy biopsy specimens) for histopathology processing
• To make salt bridges and gel plugs for use in electrochemistry.
• In formicariums as a transparent substitute for sand and a source of nutrition.
• As a natural ingredient to form modelling clay for young children to play with.
• As an allowed biofertilizer component in organic farming.
• As a substrate for precipitin reactions in immunology.