While serious effects are rare and have most often resulted from misuse, adverse reactions have occurred when used properly. The FDA, therefore, requires a so-called black box warning on lindane products, which explains the risks of lindane products and their proper use.The black box warning emphasizes that lindane should not be used on premature infants and individuals with known uncontrolled seizure disorders, and should be used with caution in infants, children, the elderly, and individuals with other skin conditions (e.g., dermatitis, psoriasis) and people who weigh less than 110 lb (50 kg), as they may be at risk of serious neurotoxicity. Environmental contamination
Lindane is a persistent organic pollutant: it is relatively long-lived in the environment, it is transported long distances by natural processes like global distillation, and it can bioaccumulate in food chains, though it is rapidly eliminated when exposure is discontinued.The production and agricultural use of lindane are the primary causes of environmental contamination, and levels of lindane in the environment have been decreasing in the U.S., consistent with decreasing agricultural usage patterns. The production of lindane generates large amounts of waste hexachlorocyclohexane isomers, and "every ton of lindane manufactured produces about nine tons of toxic waste." Modern manufacturing standards for lindane involve the treatment and conversion of waste isomers to less toxic molecules, a process known as "cracking".When lindane is used in agriculture, an estimated 12–30% of it volatilizes into the atmosphere, where it is subject to long-range transport and can be deposited by rainfall.
Development  work in the UK was accelerated because at that time in World War II imports of derris containing the insecticide rotenone were restricted owing to the Japanese occupation of Malaya and alternatives were urgently needed. In trials in 1943 it was found that a five-fold increase in the yield of oats and wheat was achieved using a dust formulation of the available material, owing to its efficacy against wireworm pests. By the end of 1945, γ-hexachlorcyclohexane of 98% purity became available and ICI commercialised a seed treatment launched in 1949 as Mergamma A, containing 1% mercury and 20% lindane. Subsequently, lindane has been used to treat food crops and forestry products, as a seed or soil treatment, and to treat livestock and pets. It was used as a household pesticide as the active pesticide ingredient of an insecticidal floor wax product called "Freewax". It has also been used as pharmaceutical treatment for lice and scabies, formulated as a shampoo or lotion. Between 1950 and 2000, an estimated 600,000 tonnes of lindane were produced globally, and the vast majority of which was used in agriculture. It has been manufactured by several countries, including the United States, China, Brazil, and several European countries, but as of 2007, only India and possibly Russia are still producing it. By November 2006, the use of lindane had been banned in 52 countries and restricted in 33 others. Seventeen countries, including the US and Canada, allowed either limited agricultural or pharmaceutical use.