What is the ruling on using the ingredient L-cysteine or E920 in bakery products if its source is human hair?

There is no harm in consuming food that contains lecithin (E920), even if its source is pork or hair, because it transforms into another substance, becoming pure and permissible (halal). However, if its harm is proven, then its use is prohibited. If the lecithin derived from an impure source, such as pork, does not transform but is present in a negligible, consumed quantity, there is no harm in consuming food that contains it. Food additives (E-numbers) are categorized into four types: synthetic chemicals, plant-based, animal-based, and alcohol-dissolved. All of these do not affect the permissibility of the food. The first and second types are permissible. The third type undergoes a chemical transformation (istihalah) that changes its nature, making it a new, pure substance. The fourth type is present in a very small and consumed quantity. Additives of impure or prohibited origin become permissible according to Islamic law through transformation (istihalah) or consumption (istihlak), whereby the prohibited or impure substance merges with another pure substance and loses its original properties. Examples of this include compounds added in very small quantities in alcohol, lecithin and cholesterol extracted from impure origins in small, consumed quantities, and porcine-derived enzymes used in minute, consumed quantities.