Shellac is a natural resin secreted by tiny insects in the genus Kerria, native to Southeast Asia and India. The insects attach themselves to tree branches, feed on sap, and secrete a hard, amber-colored resin that encases their bodies. That resin is harvested, refined, and used in an enormous range of products, from the shiny coating on your apples to the finish on antique furniture to the outer shell of many pharmaceutical tablets.
How Insects Produce Shellac
Shellac comes from several species of lac insects, all belonging to the genus Kerria. The most commercially significant are Kerria lacca in India, Kerria yunnanensis in China, Kerria chinensis in Thailand, and Kerria nepalensis in Myanmar. These tiny sap-sucking insects colonize the branches of host trees, and more than 400 tree species have been recorded as suitable hosts. The three most important are kusumr, palas, and ber trees, all common across South and Southeast Asia.
The insects feed by piercing bark and drinking tree sap. As they feed, they secrete a resinous coating that gradually covers the colony in a thick crust. This raw encrustation, called sticklac, contains three components: resin (the largest portion), a red-purple dye, and wax. The resin itself is built from two classes of molecules the insect synthesizes internally. One pathway converts compounds from digested sap into sesquiterpene acid esters. A parallel pathway produces long-chain hydroxy fatty acids. These two types of molecules link together into complex ring-shaped structures called lactones and lactides, forming the tough, film-like resin that gives shellac its distinctive properties.
From Tree Branch to Finished Product
The harvested crust of resin is first scraped from branches and crushed. This crushed material is sieved to remove twigs, insect remains, and other organic debris, then washed and air-dried. The result is called seedlac, a granular material that serves as the starting point for all further refinement.
From seedlac, manufacturers produce different grades depending on the intended use. Button lac retains its natural wax content, which gives it toughness and some moisture resistance. This makes it a preferred choice for floor finishing, interior woodwork, and French polishing musical instruments. Dewaxed shellac has the wax removed, creating a purer product that bonds well with other finishes. It works as a universal sealer or primer and as a transitional layer between dissimilar coatings like varnish, lacquer, or urethane. For pharmaceutical and food applications, shellac undergoes additional purification steps, sometimes including bleaching with hydrogen peroxide or sodium hypochlorite to produce a pale, nearly colorless product.
Chemical and Physical Properties
Chemically, shellac is a complex mixture of lactones and lactides formed from aleuritic acid (a hydroxy fatty acid) and shelloic acid (a sesquiterpene acid). The resin is rich in functional groups including carboxyl, hydroxyl, aldehyde, and double bonds, which is why it bonds readily to so many surfaces and dissolves easily in alcohol.
At room temperature, shellac is hard and brittle. It transitions to a soft, pliable state at its glass transition temperature, which falls between about 41°C and 49°C (106°F to 120°F) depending on the grade. Wax-containing varieties show a small melting peak around 76°C to 78°C. This relatively low softening point is why shellac finishes can be damaged by hot objects placed directly on them, but it also makes shellac easy to work with for coating and molding applications. The traditional way to dissolve shellac is in ethanol, typically at ratios around 7 grams of shellac flakes to 50 milliliters of alcohol.
Shellac in Food
If you’ve ever noticed the shine on an apple at the grocery store, there’s a good chance you were looking at shellac. Listed as E 904 in the European Union, shellac is authorized as a glazing agent across a wide range of food categories. It coats citrus fruit, apples, pears, peaches, pineapples, mangoes, avocados, papayas, and pomegranates. It gives chocolate products, hard candies, breath fresheners, and chewing gum their glossy finish. Coffee beans, processed nuts, and cereal-based snacks are also commonly coated with it. Even small chocolate-covered bakery items may carry a shellac glaze.
Shellac works in food because it forms a thin, flexible film that acts as a moisture barrier. It keeps fruit from drying out, prevents chocolate from developing a white bloom, and gives confections an attractive sheen. In the United States, purified shellac appears in FDA regulations under multiple food contact categories. It is applied by spraying a diluted solution (in ethanol or an alkaline base) that dries into a thin, invisible coating.
Pharmaceutical Coatings
One of shellac’s most useful properties is that it resists acidic environments but breaks down in alkaline ones. Your stomach is highly acidic (around pH 1 to 3), while your intestines are more alkaline (around pH 7 to 8). Shellac exploits this difference perfectly as an enteric coating on tablets and capsules. A shellac-coated tablet passes through the stomach intact, protecting both the drug from stomach acid and the stomach lining from the drug. Once it reaches the intestines, the alkaline environment erodes the shellac layer and releases the medication exactly where it needs to be absorbed.
This pH-dependent release mechanism makes shellac valuable for delivering not just standard drugs but also sensitive biological compounds like probiotics, enzymes, and certain nutrients that would be destroyed by stomach acid. The thickness of the shellac coating can be adjusted to control how quickly the contents are released, allowing for precise, site-specific delivery in the intestinal tract.
Wood Finishing and Cosmetics
Shellac has been used as a wood finish for centuries and remains popular among woodworkers and furniture restorers. A typical application involves dissolving flakes in ethanol, then applying thin coats with a brush or cotton cloth. The first set of coats dries in about 30 minutes, after which the surface is lightly sanded. Additional sets of coats, with longer drying intervals of four hours to overnight, build up a warm, lustrous finish. The final surface can be burnished to a high gloss. Shellac finishes are prized for their clarity, warmth, and ability to enhance the natural grain of wood.
In cosmetics, shellac appears in mascaras, eyeliners, hair sprays, and nail products. The “shellac” branding on certain gel nail polishes borrows the name but uses synthetic formulations rather than natural insect resin. Actual shellac resin does appear in some cosmetic formulations as a film-forming agent, particularly in products applied to eyelids and lips.
Allergic Reactions
Shellac is a recognized contact allergen, though reactions are relatively uncommon in the general population. In a Spanish study that patch-tested 980 patients suspected of cosmetic-related contact dermatitis, about 3.8% tested positive for a shellac allergy. Most cases were linked to cosmetics applied to the eyelids and lips. Two cases had an occupational connection to food handling, where workers came into repeated contact with shellac-coated products. Symptoms typically present as contact dermatitis: redness, itching, and irritation at the site of exposure.
Why Shellac Isn’t Vegan
Because shellac is produced by living insects, it is classified as an animal-derived product. Lac insects fall within the Kingdom Animalia, and harvesting the resin inevitably kills large numbers of insects in the process, since the colonies are scraped from branches while insects are still embedded in the resin. For this reason, most vegans avoid products containing shellac. This can be surprisingly tricky, since shellac appears in products where you might not expect it: coated fruit, shiny candy, pharmaceutical tablets, and cosmetics. On ingredient labels, look for “shellac,” “confectioner’s glaze,” “resinous glaze,” “pharmaceutical glaze,” or E 904.