allantoin

n. extract of plants which soothes and heals (used in creams and topical substances concocted for medical purposes for the skin); substance present in allantoic fluid and also in the fetal urine of some mammals

Allantoin is a chemical compound with formula C4H6N4O3. It is also called 5-ureidohydantoin or glyoxyldiureide. It is a diureide of glyoxylic acid. Named after the allantois, an amniote embryonic excretory organ in which it concentrates during development in most mammals except higher apes, it is a product of oxidation of uric acid by purine catabolism. After birth, it is the predominant means by which nitrogenous waste is excreted in the urine of these animals. In humans and other higher apes, the metabolic pathway for conversion of uric acid to allantoin has been lost, so the former is excreted. Recombinant rasburicase is sometimes used as a drug to catalyze this metabolic conversion in patients. In fish, allantoin is broken down further (into ammonia) before excretion, but most of the enzymes responsible have been lost in mammals [1]. Allantoin is a major metabolic intermediate in many other organisms including plants and bacteria.
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Allantoin /al·lan·to·in/ a crystalline substance found in allantoic fluid, fetal urine, many plants, and produced synthetically; used topically as [more]Allantoin - Community and Resources

(n.)
A crystalline, transparent, colorless substance found in the allantoic liquid of the fetal calf; -- formerly called allantoic acid and amniotic acid.
  

noun
powder from the herb comfrey, used to treat skin disorders