Reverse smoking, where the lit end of the cigarette is held in the mouth is also associated with mucosal changes. Tobacco chewing, e.g. betel leaf and areca nut, called paan, tends to produce a distinctive white patch in a buccal sulcus termed "tobacco pouch keratosis". In the majority of persons, cessation triggers shrinkage or disappearance of the lesion, usually within the first year after stopping. Alcohol
Although the synergistic effect of alcohol with smoking in the development of oral cancer is beyond doubt, there is no clear evidence that alcohol is involved in the development of leukoplakia, but it does appear to have some influence. Excessive use of a high alcohol-containing mouth wash (> 25%) may cause a grey plaque to form on the buccal mucosa, but these lesions are not considered true leukoplakia. Sanguinaria
Sanguinaria (Bloodroot) is a herbal extract that is included in some toothpastes and mouthwashes. Its use is strongly associated with development of leukoplakia, usually in the buccal sulcus. This type of leukoplakia has been termed "sanguinaria associated keratosis" and more than 80% of people with leukoplakia in the vestibule of the mouth have used this substance. Upon stopping contact with the causative substance, the lesions may persist for many years. Although this type of leukoplakia may show dysplasia, the potential for malignant transformation is unknown. Ultraviolet radiation
Ultraviolet radiation is believed to be a factor in the development of some leukoplakia lesions of the lower lip, usually in association with actinic cheilitis.
Mutations in the ASS gene reduce the activity of the enzyme, which disrupts the urea cycle and prevents the body from processing nitrogen effectively. Excess nitrogen, in the form of ammonia, and other byproducts of the urea cycle, accumulate in the bloodstream, leading to the characteristic features of type I citrullinemia. Type II
The symptoms of type II citrullinemia (Online Mendelian Inheritance in Man (OMIM): 605814 and Online Mendelian Inheritance in Man (OMIM): 603471) usually appear during adulthood and mainly affect the central nervous system. Characteristic features include confusion, abnormal behaviors (such as aggression, irritability, and hyperactivity), seizures, and coma. Specific investigation like decrease citrulline level , increase ammonium ion . These symptoms can be life-threatening, and are known to be triggered by certain medications, infections, and alcohol intake in people with this type.Type II citrullinemia may also develop in people who had a liver disorder called neonatal cholestasis during infancy. This condition blocks the flow of bile and prevents the body from processing certain nutrients properly. In many cases, the  symptoms resolve within a year. Years or even decades later, however, some of these people develop the characteristic features of adult type II citrullinemia.Type II citrullinemia is primarily found in the Japanese population, where it occurs in an estimated one in 100,000 to 230,000 individuals. Type II has also been reported in people from East Asian and Middle Eastern populations. Mutations in the SLC25A13 gene are responsible for type II citrullinemia.