Shellac
Scientific Name(s): Laccifer lacca
Common Name(s): Gommelaque, Lac, Lacca, Shellac
Medically reviewed by Drugs.com. Last updated on Jan 23, 2024.
Clinical Overview
Use
The most common use is as a furniture finish, but it has also been used in the pharmaceutical industry, in dentistry, and in cosmetics.
Dosing
There is no clinical evidence to support specific doses of shellac for therapeutic purposes.
Contraindications
Contraindications have not yet been identified.
Pregnancy/Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Interactions
None well documented.
Adverse Reactions
Several cases of allergic contact dermatitis of the eyelids due to shellac in mascara, cheilitis due to shellac in lip products, allergic dermatitis due to shellac in a hairspray, and allergic dermatitis in black ink most likely containing shellac for tattooing have been reported.
Toxicology
Shellac NF is food grade and is listed as Generally Recognized as Safe (GRAS) by the FDA.
Scientific Family
- Coccidae
Source
Shellac is the purified product of lac, the red, hardened secretion of the insect Laccifer (Tachardia) lacca Kerr. This tiny insect sucks the sap of selected trees and bushes and secretes lac as a protective covering. The name lac is said to derive from lakh, the Sanskrit word for one hundred thousand, a reference to the very large number of insects involved in producing appreciable amounts of the product.(Yates 1970)
Lac is cultivated in India, Thailand, and Burma. The whitest lac is produced by insects infesting the kusum tree (Schleichera trijuga). The harvester cuts twigs coated with lac into small pieces called sticklac. The crude material is ground and soaked in water to remove debris and insect bodies. The remaining material is soaked in sodium carbonate, which removes laccaic acid, a complex mixture of at least four structurally related pigments. The resulting granules retain the yellow pigment erythrolaccin and are dried to form seedlac. Further treatment by melting, evaporating, or filtering yields shellac.(Der Marderosian 1988)
History
Shellac is most often used as a finish for fine furniture. Further, the material has been used for almost 100 years by the pharmaceutical industry. Examples of shellac's role in this field include: Tablet coating formulations,(Alam 1972, Pandula 1970, Tuerck 1973) microencapsulation,(Labhasetwar 1989, Labhasetwar 1990, Sheorey 1991) matrix formation,(Serajuddin 1984) and humidity tolerance.(Gürsoy 1986)
Shellac is used in dentistry, as a binding agents for dentures, restorations, and mouldings, and for training purposes in dental schools.(Azouka 1993, Escoe 1989, Harrison 1995, Heath 1993, Hitge 1989, Lee 1991, Lie 1987)
Shellac has also been used as an ingredient in hair spray and in other cosmetics, like mascara and lipstick and as a tackifier in eye makeup.(Huang 2021) However, shellac undergoes an aging effect upon storage and thus has fallen into disfavor as an ingredient in some preparations.(Der Marderosian 1988)
Chemistry
The National Formulary XV recognizes 4 grades of shellac: Orange, dewaxed orange, regular bleached and refined wax-free bleached. The grades differ in the manner in which the seedlac is treated. Orange shellac is obtained by the evaporation of filtered ethanolic solutions of seedlac. It may be dewaxed by further filtration. Regular bleached shellac is obtained by dissolving the seedlac in aqueous sodium carbonate at a high temperature. After filtration, a bleaching agent (such as sodium hypochlorite) is added. The resin is removed by sulfuric acid precipitation. Refined wax-free bleached shellac adds another filtration step to remove the waxes.(American Pharmaceutical Association 1955)
The exact chemical composition of shellac is unknown. It appears to be composed of a network of hydroxy fatty acid esters and sesquiterpene acid esters with a molecular weight of about 1000. Aleuretic acid, r-butolic acid, shellolic acid, and jalaric acid are the major constituents. The composition is a function of the source and time of harvest of the sticklac. Variability in the product may be a problem for commercial users of shellac. The physical properties of shellac also vary. For example, the reported melting point ranges from 77° to 120°C. Shellac is soluble in ethanol, methanol, glycols, glycol ethers, and alkaline water.(Yates 1970)
Uses and Pharmacology
Gangrene
Clinical data
A 1-year prospective, randomized, controlled trial was conducted to determine the ability of shellac to prevent infection and progression of dry gangrene to wet gangrene in 26 patients with type 2 diabetes. The patients presented with peripheral dry, well-demarcated gangrene in their feet and were awaiting nonsurgical autoamputation because of contraindications to revascularization or surgery, limited life expectancy, and/or refusal of surgical amputation. Compared to conventional treatment with 10% povidone-iodine, the slightly lower rate of surgical amputation in the shellac group (46.2% vs 60%) was not statistically significant. None of the patients in the shellac group developed an allergic reaction.(Alzahrani 2013)
Other uses
Animal data
In a study of rats, shellac included with a high fat diet was found to prevent increases in body weight and was associated with a reduction in serum leptin levels compared to the group only receiving a high fat diet (P<0.05 for both comparisons). Shellac was also associated with a reduction in triglyceride levels and increase in high-density lipoprotein levels (P<0.05 for both comparisons).(Poorassar 2020)
Clinical data
A randomized double-blind, controlled, clinical study evaluated the efficiency of shellac in reducing dentin hypersensitivity, which appeared to be as effective as the control agents tested.(Hoang-Dao 2009)
Dosing
There is no clinical evidence to support specific doses of shellac for therapeutic purposes.
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Interactions
None well documented.
Adverse Reactions
Allergy and contact dermatitis, including eyelid dermatitis, have been reported.(Das 2011, Huang 2021, Schalock 2020, Veverka 2018, Warshaw 2021)
Several cases of allergic contact dermatitis or eczema of the eyelids in women using mascara (Great Lash, Diorshow) have been documented with confirmed positive sensitivity to shellac through breakdown analysis of the product ingredients.(Gallo 2005, Le Coz 2002)
A case involving a patient with an allergy to shellac experienced an allergic reaction after getting a tattoo with black ink. Shellac is often used as a binding agent in black inks used for tattoos.(Gonzalez-Villanueva 2016)
Five cases of cheilitis resulting from use of a lip product containing shellac has been reported.(Orton 2001)
A case of allergic contact dermatitis due to a shellac-containing hairspray was reported in a female with frontal fibrosing alopecia.(Navarro-Trivino 2022)
Toxicology
Studies suggest cytotoxicity is low.(Lu 2014) Shellac NF is food grade and is listed as Generally Recognized as Safe (GRAS) by the FDA.(CFR 2022)
Index Terms
- Laccifer (Tachardia) lacca Kerr.
References
Disclaimer
This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.
This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.
Further information
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