Choline  is an essential nutrient for humans and many other animals. Choline occurs as a cation that forms various salts (X− in the depicted formula is an undefined counteranion). To maintain health, it must be obtained from the diet as choline or as choline phospholipids, like phosphatidylcholine. Humans, as well as most other animal species, do make choline de novo; however, production is generally insufficient. Choline is often not classified as a vitamin, but as a nutrient with an amino acid–like metabolism. In most animals, choline phospholipids are necessary components in cell membranes, in the membranes of cell organelles, and in very low-density lipoproteins. Choline is required to produce acetylcholine – a neurotransmitter – and S-adenosylmethionine (SAM), a universal methyl donor. Upon methylation SAM is transformed into homocysteine. Symptomatic choline deficiency – rare in humans – causes nonalcoholic fatty liver disease and muscle damage. Excessive consumption of choline (greater than 7.5 g/day) can cause low blood pressure, sweating, diarrhea and fish-like body odor due to trimethylamine, which forms in its metabolism. Rich dietary sources of choline and choline phospholipids include organ meats and egg yolks, dairy products, peanuts, certain beans, nuts, seeds and vegetables with pasta and rice also contributing to choline intake in the American diet. Chemistry
The cholines are a family of water-soluble quaternary ammonium compounds. Choline is the parent compound of the cholines class, consisting of ethanolamine having three methyl substituents attached to the amino function. Choline hydroxide is known as choline base.
Other side effects include nausea, vomiting, dizziness, tiredness and headache. There are however also severe side effects including severe allergic reactions, like (nettle) rash, itch, tightness in chest, difficult breathing and swelling in either the face, mouth, lips or tongue. Other severe side effects include bloody or severe diarrhea, fever, joint pain, red, blistered or swollen skin and stomach pain. In the eye, it can cause conjunctivitis. There are also life-threatening conditions which can be produced by the antibiotic, like Stevens Johnson syndrome and Erythema multiforme. Higher exposure can also cause unconsciousness. One case showed that sulfacetamide eyedrops can very rarely cause life-threatening skin condition toxic epidermal necrolysis (TEN). These are however not all side effects. For more information the health care provider can be contacted. Sulfacetamide should not be used by individuals who have a sensitivity to sulfur or sulfa. Toxicity
The acute oral toxicity (LD50) in a mouse is 16.5 g/kg. As this falls within Toxicity Category IV of the toxicity category rating for oral administration, it is practically non-toxic and also not an irritant when taken in orally. However, it is very hazardous in case of skin contact (irritant), ingestion and inhalation. Research proved that it is more toxic in the presence of light than in the dark. Sulfacetamide is slightly irritant when UV-A light is present. In the presence of light sulfacetamide gets sensitized and degraded which might cause irritation which will lead to toxicity when it is used continuously. In the dark only slight irritation has been shown.