皮肤科以含有尿素的某些药剂来提高皮肤的湿度。非手术摘除的指甲使用的封闭敷料中，含有40%的尿素。

　　测试幽门螺杆菌存在的碳-14-呼气试验，使用了含有碳14或碳13标记的尿素。因为幽门螺杆菌的尿素酶使用尿素来制造氨，以提高其周边胃里的pH值。同样原理也可测试生活在动物胃中的类似细菌。

　　农业应用：

　　尿素是一种高浓度氮肥，属中性速效肥料，也可用于生产多种复合肥料。在土壤中不残留任何有害物质，长期施用没有不良影响。畜牧业可用作反刍动物的饲料。 但在造粒中温度过高会产生少量缩二脲，又称双缩脲，对作物有抑制作用。我国规定肥料用尿素缩二脲含量应小于0.5%。缩二脲含量超过1%时，不能做种肥，苗肥和叶面肥，其他施用期的尿素含量也不宜过多或过于集中。

　　尿素是有机态氮肥，经过土壤中的脲酶作用，水解成碳酸铵或碳酸氢铵后，才能被作物吸收利用。因此，尿素要在作物的需肥期前4～8天施用。

　　商业应用：

　　特殊塑料的原料，尤其尿素甲醛树脂

　　某些胶类的原料

　　肥料和饲料的成分

　　取代防冻的盐撒在街道，优点是不使金属腐蚀

　　加强香烟的气味

　　赋予工业生产的椒盐卷饼棕色

　　某些洗发剂、清洁剂的成分

　　急救用制冷包的成分，因为尿素与水的反应会吸热

　　处理柴油机、发动机、热力发电厂的废气，尤其可降低其氧化氮

　　催雨剂的成分〈配合盐〉

　　过去用来分离石蜡，因为尿素能形成包合物

　　耐火材料

　　环保引擎燃料的成分

　　美白牙齿产品的成分

　　为化学肥料

　　染色和印刷时的重要辅助剂

　　实验室应用：

　　尿素能非常有效的使蛋白质变性，尤其能非常有效地破坏非共价键结合的蛋白质。这特点可以提高某些蛋白质的可溶性，其浓度可达10摩尔/体积。尿素也可用来制造硝酸尿素。

　　饲料添加剂：

　　人类粮食资源与蛋白质的短缺，也造成饲料工业一大难题。业者积极寻找蛋白质的新来源，并扩及蛋白质以外的氮来源，例如含氮量高的尿素。

　　1897年，Waesk 等人提出反刍动物能转化非蛋白质氮为菌体蛋白质的想法。1949年，C. J. Watson 等人喂食绵羊含有N15标记的尿素胶囊，4天后在绵羊血液、肝脏、肾脏中检验出含有N15的蛋白质。这证实了反刍动物可以利用非蛋白质氮。同年 J. K. Looli 等人以尿素当作唯一氮源喂食绵羊，发现绵羊能够正氮平衡，表明绵羊瘤胃里的微生物能利用尿素合成其生长所需的10种必需氨基酸。自此，尿素及尿素化合物成为反刍动物的饲料添加剂了。

　　在化妆品中的应用：

　　尿素是一种很好用的保湿成分，它就存在于肌肤的角质层当中，属于肌肤天然保湿因子NMF的主要成分。对肌肤来说，尿素具有保湿以及柔软角质的功效，所以也能够防止角质层阻塞毛细孔，藉此改善粉刺的问题。用于面膜、护肤水、膏霜、护手霜等产品中保湿成份的添加。添加比例为3-5%。

　　工业应用：

　　对钢铁、不锈钢化学抛光有增光作用，在金属酸洗中用作缓蚀剂，也用于钯活化液的配制。

Agriculture

More than 90% of world production of urea is destined for use as a nitrogen-release fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has the lowest transportation costs per unit of nitrogen nutrient. The standard crop-nutrient rating of urea is 46-0-0.

Many soil bacteria possess the enzyme urease, which catalyzes the conversion of the urea molecule to two ammonia molecules and one carbon dioxide molecule, thus urea fertilizers are very rapidly transformed to the ammonium form in soils. Among soil bacteria known to carry urease, some ammonia-oxidizing bacteria (AOB), such as species of Nitrosomonas, are also able to assimilate the carbon dioxide released by the reaction to make biomass via the Calvin Cycle, and harvest energy by oxidizing ammonia (the other product of urease) to nitrite, a process termed nitrification.^[10] Nitrite-oxidizing bacteria, especially Nitrobacter, oxidize nitrite to nitrate, which is extremely mobile in soils and is a major cause of water pollution from agriculture. Ammonia and nitrate are readily absorbed by plants, and are the dominant sources of nitrogen for plant growth. Urea is also used in many multi-component solid fertilizer formulations. Urea is highly soluble in water and is, therefore, also very suitable for use in fertilizer solutions (in combination with ammonium nitrate: UAN), e.g., in 'foliar feed' fertilizers. For fertilizer use, granules are preferred over prills because of their narrower particle size distribution, which is an advantage for mechanical application.

The most common impurity of synthetic urea is biuret, which impairs plant growth.

Urea is usually spread at rates of between 40 and 300 kg/ha but rates vary. Smaller applications incur lower losses due to leaching. During summer, urea is often spread just before or during rain to minimize losses from volatilization (process wherein nitrogen is lost to the atmosphere as ammonia gas). Urea is not compatible with other fertilizers.

Because of the high nitrogen concentration in urea, it is very important to achieve an even spread. The application equipment must be correctly calibrated and properly used. Drilling must not occur on contact with or close to seed, due to the risk of germination damage. Urea dissolves in water for application as a spray or through irrigation systems.

In grain and cotton crops, urea is often applied at the time of the last cultivation before planting. In high rainfall areas and on sandy soils (where nitrogen can be lost through leaching) and where good in-season rainfall is expected, urea can be side- or top-dressed during the growing season. Top-dressing is also popular on pasture and forage crops. In cultivating sugarcane, urea is side-dressed after planting, and applied to each ratoon crop.

In irrigated crops, urea can be applied dry to the soil, or dissolved and applied through the irrigation water. Urea will dissolve in its own weight in water, but it becomes increasingly difficult to dissolve as the concentration increases. Dissolving urea in water is endothermic, causing the temperature of the solution to fall when urea dissolves.

As a practical guide, when preparing urea solutions for fertigation (injection into irrigation lines), dissolve no more than 30 kg urea per 100 L water.

In foliar sprays, urea concentrations of 0.5% – 2.0% are often used in horticultural crops. Low-biuret grades of urea are often indicated.

Urea absorbs moisture from the atmosphere and therefore is typically stored either in closed/sealed bags on pallets or, if stored in bulk, under cover with a tarpaulin. As with most solid fertilizers, storage in a cool, dry, well-ventilated area is recommended.

Chemical industry

Urea is a raw material for the manufacture of many important chemical compounds, such as

• Various plastics, especially the urea-formaldehyde resins.
• Various adhesives, such as urea-formaldehyde or the urea-melamine-formaldehyde used in marine plywood.
• Potassium cyanate, another industrial feedstock.

Explosive

Urea can be used to make urea nitrate, a high explosive that is used industrially and as part of some improvised explosive devices.

 Automobile systems

Urea is used in SNCR and SCR reactions to reduce the NO_x pollutants in exhaust gases from combustion from diesel, dual fuel, and lean-burn natural gas engines. The BlueTec system, for example, injects water-based urea solution into the exhaust system. The ammonia produced by the hydrolysis of the urea reacts with the nitrogen oxide emissions and is converted into nitrogen and water within the catalytic converter.

 Other commercial uses

• A stabilizer in nitrocelluloseexplosives
• A component of animal feed, providing a relatively cheap source of nitrogen to promote growth
• A non-corroding alternative to rock salt for road de-icing, and the resurfacing of snowboarding halfpipes and terrain parks
• A flavor-enhancing additive for cigarettes
• A main ingredient in hair removers such as Nair and Veet
• A browning agent in factory-produced pretzels
• An ingredient in some skin cream,^[11] moisturizers, hair conditioners
• A reactant in some ready-to-use cold compresses for first-aid use, due to the endothermic reaction it creates when mixed with water
• A cloud seeding agent, along with other salts
• A flame-proofing agent, commonly used in dry chemical fire extinguisher charges such as the urea-potassium bicarbonate mixture
• An ingredient in many tooth whitening products
• An ingredient in dish soap
• Along with ammonium phosphate, as a yeast nutrient, for fermentation of sugars into ethanol
• A nutrient used by plankton in ocean nourishment experiments for geoengineering purposes
• As an additive to extend the working temperature and open time of hide glue
• As a solubility-enhancing and moisture-retaining additive to dye baths for textile dyeing or printing

Laboratory uses

Urea in concentrations up to 10 M is a powerful proteindenaturant as it disrupts the noncovalent bonds in the proteins. This property can be exploited to increase the solubility of some proteins. A mixture of urea and choline chloride is used as a deep eutectic solvent, a type of ionic liquid.

Urea can in principle serve as a hydrogen source for subsequent power generation in fuel cells. Urea present in urine/wastewater can be used directly (though bacteria normally quickly degrade urea.) Producing hydrogen by electrolysis of urea solution occurs at a lower voltage (0.37V) and thus consumes less energy than the electrolysis of water (1.2V).

Urea in concentrations up to 8 M can be used to make fixed brain tissue transparent to visible light while still preserving florescent signals from labeled cells. This allows for much deeper imaging of neuronal processes then previously obtainable using conventional one photon or two photon confocal microscopes.^[13]

 Medical use

Urea-containing creams are used as topical dermatological products to promote rehydration of the skin. Urea 40% is indicated for psoriasis, xerosis, onychomycosis, ichthyosis, eczema, keratosis, keratoderma, corns, and calluses. If covered by an occlusive dressing, 40% urea preparations may also be used for nonsurgical debridement of nails. Urea 40% "dissolves the intercellular matrix"^[14] of the nail plate. Only diseased or dystrophic nails are removed, as there is no effect on healthy portions of the nail. This drug is also used as an earwax removal aid. Urea can also be used as a Diuretic.

Certain types of instant cold packs (or ice packs) contain water and separated urea crystals. Rupturing the internal water bag starts an endothermic reaction and allows the pack to be used to reduce swelling.

Like saline, urea injection is used to perform abortions.

Urea is the main component of an alternative medicinal treatment referred to as urine therapy.

The blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood that comes from urea. It is used as a marker of renal function.

Urea labeled with carbon-14 or carbon-13 is used in the urea breath test, which is used to detect the presence of the bacteria Helicobacter pylori (H. pylori) in the stomach and duodenum of humans, associated with peptic ulcers. The test detects the characteristic enzyme urease, produced by H. pylori, by a reaction that produces ammonia from urea. This increases the pH (reduces acidity) of the stomach environment around the bacteria. Similar bacteria species to H. pylori can be identified by the same test in animals such as apes, dogs, and cats (including big cats).

 Analysis

Urea is readily quantified by a number of different methods, such as the diacetyl monoxime colorimetric method, and the Berthelot reaction (after initial conversion of urea to ammonia via urease). These methods are amenable to high throughput instrumentation, such as automated flow injection analyzers^[15] and 96-well micro-plate spectrophotometers.^[