Shun NagaiEggshell membrane is the thin layer found on the inside of a chicken eggshell—the transparent film you can see when peeling a hard-boiled egg (see photo above). In recent years, eggshell membrane has drawn attention as a functional ingredient in pet food, particularly for its potential joint-support benefits.
Eggshell membrane is known to contain many compounds associated with joint care, including collagen and glucosamine, and it is already being added to supplements formulated for canine joint support. Below, we clearly explain its basic composition, usefulness for dogs, safety, and how it compares with other ingredients, based on the latest research findings.
Composition and Characteristics of Eggshell Membrane
Eggshell membrane is composed primarily of protein, especially fibrous collagen. Chemical analyses show that eggshell membrane powder contains about 40–60% protein, of which roughly 10–25% is collagen. It also contains sugar-chain components collectively known as glycosaminoglycans (GAGs), including sulfated polysaccharides such as chondroitin sulfate and dermatan sulfate.
In addition, eggshell membrane contains hyaluronic acid and glucosamine (a type of hexosamine), which are components of synovial fluid and cartilage. Trace components such as sialic acid, desmosine (an elastin-derived amino acid), lysyl oxidase, and lysozyme (an enzyme) have also been identified. One of the major distinguishing features of eggshell membrane is this combination of diverse bioactive components.
Components Found in Eggshell Membrane
| Component | Content | Main Function |
|---|---|---|
| Total protein | 40–60% | Structural formation and tissue repair |
| Collagen | 10–25% | Fiber formation and joint protection |
| Chondroitin sulfate | Up to 2% | Joint lubrication and cartilage protection |
| Hyaluronic acid | Up to 2% | Water retention and cushioning |
| Glucosamine | Up to 1% | Synthesis of cartilage matrix |
- Collagen:
A major structural protein in eggshell membrane fibers. It forms a tough fibrous structure and contributes to maintaining the structure of joints and skin. Eggshell membrane may contain up to about 25% collagen by dry weight. - Protein (other proteins):
In addition to collagen, eggshell membrane contains many other proteins, including keratin-like proteins. Total protein content accounts for around half of its composition. - Glycosaminoglycans (GAGs):
These include chondroitin sulfate (up to 2%), hyaluronic acid (up to 2%), dermatan sulfate, and others. They are components of proteoglycans, the major constituents of cartilage, and help support joint elasticity and lubrication. Glycosaminoglycans derived from eggshell membrane are considered useful for maintaining joint tissue health. - Glucosamine:
A type of amino sugar present in small amounts (up to 1%) in eggshell membrane. It serves as a building block for cartilage matrix and synovial fluid. - Other components:
Reported minor constituents include sialic acid (a glycoprotein component), desmosine and isodesmosine (cross-linking amino acids derived from elastin), ovotransferrin, lysozyme, and N-acetylglucosaminidase. Although present only in trace amounts, these compounds may contribute to biological regulation and antimicrobial activity.
As described above, eggshell membrane is a natural material that contains a balanced mix of collagen, GAGs, and amino acids, making it rich in compounds beneficial for joints. In fact, it has attracted attention as an ingredient capable of supplying collagen, glucosamine, chondroitin sulfate, hyaluronic acid, and other joint-building components all at once. These combined constituents are thought to offer anti-inflammatory and tissue-regenerative effects.
Eggshell membrane ingredients are typically produced by separating and drying the inner membrane from eggshells, which are by-products of edible egg processing. Untreated raw eggshell membrane is not easily digested or absorbed, so industrial products are usually partially hydrolyzed enzymatically into peptide forms to improve bioavailability. An example is NEM®, a natural eggshell membrane-derived ingredient.
In the case of NEM®, a 500 mg serving is said to provide the equivalent of the eggshell membrane from about 12 eggs. This illustrates how lightweight yet nutrient-dense eggshell membrane is, and it also means that relatively small inclusion levels in pet food can provide sufficient amounts of functional compounds.
Scientific Evidence for Joint Care Benefits in Dogs
Because of its composition, eggshell membrane has been studied as an ingredient that may improve arthritis and joint function. In recent years, several clinical studies have also reported its effectiveness in dogs.
Effects of Eggshell Membrane Supplements in Dogs With Arthritis
One representative study was a multicenter, randomized, double-blind, placebo-controlled trial conducted in the United States. It involved 51 dogs with mild to moderate joint dysfunction and evaluated supplementation over a six-week period.
Dogs in the treatment group received an eggshell membrane-derived ingredient (NEM®) daily at a dose of approximately 13.5 mg per kg of body weight, while the control group received a placebo. As a result, the eggshell membrane group showed improvements of about 20% in both joint pain score and function score after just one week, with statistically significant improvements compared with the placebo group.
After six weeks of continued supplementation, the treatment group also showed significant improvement in quality-of-life (QOL) scores and in veterinarian-assessed joint pain indicators compared with the placebo group. Interestingly, blood levels of CTX-II, a marker of cartilage breakdown, fell by 47.9% in the treatment group and improved significantly relative to the placebo group.
The researchers described this as a “marked chondroprotective effect,” suggesting that eggshell membrane may help not only relieve symptoms but also suppress breakdown of joint tissue.
Other Clinical Studies and Overall Evaluation
In addition to studies of eggshell membrane as a standalone ingredient, benefits have also been reported for joint-care supplements containing eggshell membrane. For example, a 2025 study evaluated a multi-ingredient supplement given for 90 days to dogs with arthritis. The supplement contained eggshell membrane (ESM), krill (as a source of omega-3 fatty acids), hyaluronic acid, Boswellia extract, astaxanthin, and other ingredients, and was compared with a placebo.
Of the 52 dogs enrolled, 46 completed the study. The eggshell membrane-containing supplement group showed significant improvement throughout the study period in measures of pain and mobility, including the CBPI pain interference score. In particular, the difference between groups for pain-related interference with daily life was statistically significant (p = 0.009). Overall, the study concluded that the supplement improved mobility and quality of life in dogs with osteoarthritis (OA).
Other pilot trials in dogs and additional reports on prolonged eggshell membrane supplementation have also suggested reductions in inflammatory markers and improvements in range of motion, further supporting the usefulness of eggshell membrane for canine joint health.
Considerations Regarding the Mechanism of Action
Several hypotheses have been proposed to explain why eggshell membrane may produce these effects. Chondroitin sulfate and hyaluronic acid in eggshell membrane may help support joint lubrication and reconstruction of the cartilage matrix, while collagen and amino acids may serve as repair materials for cartilage cells, thereby promoting tissue repair.
Eggshell membrane-derived compounds have also been reported to have anti-inflammatory effects, possibly reducing joint pain and stiffness by suppressing inflammatory cytokines. In fact, human clinical studies have shown that oral administration of 500 mg/day of eggshell membrane significantly reduced joint pain and stiffness within seven days, with further improvement after 30 days of continued use.
This relatively rapid onset of action appears to differ from supplementation with glucosamine or chondroitin alone, which generally takes longer to show effects. It is believed that the combined actions of eggshell membrane—both chondroprotective and anti-inflammatory—work synergistically.
Reduced Allergenicity, Safety, and Precautions for Use
Because eggshell membrane is derived from chicken eggs, attention must be paid to its relationship with egg allergy. In general, the eggshell itself is considered not to contain the major egg allergens found in egg white proteins, but when the membrane is included, allergenic proteins may still be present, so caution is needed.
In fact, suppliers of eggshell membrane ingredients such as NEM® explicitly state that it should not be used in pets with egg allergies, and they report that even after more than 10 years on the market, no health problems other than egg-allergy-related concerns have been reported. Therefore, the most important rule is that dogs with egg allergies should not be given products containing eggshell membrane.
For dogs without egg allergies, however, eggshell membrane is generally considered a safe ingredient. Hydrolyzed eggshell membrane peptides have lower molecular weights and are easier to digest and absorb, which is expected to reduce allergenicity as well. Even so, products should still clearly indicate that the ingredient is egg-derived.
Under Japanese food labeling law, when “eggshell membrane” is listed as an ingredient, allergen labeling indicating that it contains egg is required. Likewise, in pet food development, as with human food products, packages and inserts should clearly indicate that eggshell membrane is an egg-derived ingredient and should warn against use in pets with egg allergies.
The allergenic risk of eggshell membrane itself is thought to be low, but not absolutely zero. Eggshell membrane may contain trace amounts of egg-white-derived enzymes such as lysozyme and other proteins, so even very small quantities could potentially trigger a reaction in animals with severe egg hypersensitivity.
Manufacturing processes should therefore minimize and remove allergenic proteins as much as possible through sufficient washing and purification. Fortunately, safety studies have shown that even high-dose administration of eggshell membrane produced no toxicity or adverse events, and no allergic reactions have been reported other than in individuals already allergic to egg.
In North America, eggshell membrane has been evaluated as GRAS (Generally Recognized as Safe) by an independent expert panel and has also been approved for use in foods for humans. This supports the view that properly manufactured and well-controlled eggshell membrane ingredients are highly safe under normal conditions of use.
Effects of Eggshell Membrane on Skin and Coat
Eggshell membrane may also have positive effects on skin and coat health in addition to joint support. It contains collagen, hyaluronic acid, sialic acid, and other compounds involved in skin hydration and elasticity. Human studies have suggested benefits such as improved skin moisture retention and enhanced hair quality and regeneration.
For example, some preliminary reports have found that oral eggshell membrane supplementation increased skin moisture and reduced wrinkles, suggesting cosmetic benefits through stimulation of collagen production and anti-inflammatory effects. Based on such findings, eggshell membrane extract is increasingly used in skincare products for humans, including creams and beauty supplements.
In dogs as well, collagen peptides and hyaluronic acid from eggshell membrane may contribute to skin barrier function and coat gloss. Within the pet food industry, eggshell membrane is attracting attention not only for joint care but also as a broader anti-aging ingredient, and it is beginning to appear in products marketed for “skin and coat care.”
The amino acids in eggshell membrane, such as proline and glycine, serve as raw materials for collagen synthesis and may support skin turnover. Hyaluronic acid and chondroitin sulfate may help maintain dermal hydration and flexibility, potentially reducing dryness and dander. In addition, because eggshell membrane-derived compounds may have anti-inflammatory activity, they could potentially play a supportive role in improving inflammatory skin conditions such as atopic dermatitis.
Pet owners have also reported positive experiences such as “my dog’s coat became shinier after using a supplement containing eggshell membrane” and “my senior dog’s skin condition improved.” These reports fall more into the category of user reviews than formal evidence, but such positive feedback does exist.
That said, clinical evidence for effects on skin and coat in dogs is not yet as well established as the evidence for joint benefits. For product developers, it may therefore be best to position eggshell membrane primarily as a joint-care ingredient, while noting that it may also provide additional support for maintaining healthy skin and coat. As more evidence accumulates, it may eventually become possible to differentiate products as comprehensive joint-plus-skin-and-coat supplements.
Potential Risks Associated With Eggshell Membrane Use
Eggshell membrane is a relatively safe ingredient, but there are still some potential risks and points of caution that should be understood during product development.
Digestibility and Gastrointestinal Effects
Eggshell membrane itself contains poorly digestible collagen fibers, so if it is given in large amounts without processing, it may cause digestive upset. In fact, reports indicate that feeding coarsely crushed eggshells (shell plus membrane) may cause diarrhea or vomiting in dogs.
For this reason, eggshell membrane should ideally be incorporated in a finely powdered or hydrolyzed form to improve digestibility and absorption. Hydrolyzed eggshell membrane peptides have better digestibility than non-hydrolyzed materials and reduce the burden on the canine digestive tract.
Risks of Excessive Intake
No serious toxicity has been reported for eggshell membrane itself, and high-dose safety has been confirmed in mouse studies and 90-day repeated-dose trials. In human use, the acceptable daily intake (ADI) has been set as high as 14 g per day. Therefore, even in dogs, there is probably little concern about acute toxicity if somewhat more than the intended amount is consumed within a normal range.
That said, excessive intake is unlikely to provide additional benefit and may simply go unabsorbed, with only a slight increase in digestive burden or the risk of soft stools. In particular, if fine eggshell particles (calcium) remain mixed into the eggshell membrane ingredient, excessive intake could raise concern about excessive calcium intake.
Excess calcium can increase the risk of skeletal abnormalities during growth and urinary stone formation, so attention should be paid to the calcium content of eggshell membrane ingredients. Pure membrane alone generally contains only negligible calcium, but depending on the manufacturing process, shell particles may remain.
Side Effects and Interactions
As noted above, reports of side effects from eggshell membrane itself are extremely limited. Clinical trials found no difference in adverse events compared with placebo, and the ingredient has been described as highly well tolerated. In rare cases, temporary soft stools or mild appetite reduction may occur initially, but experience suggests these effects tend to stabilize with continued use.
As for interactions, eggshell membrane has a long record of being used alongside other supplement ingredients, and no specific risks of interaction with particular drugs or ingredients have been reported at this time.
Raw Material Quality and Hygiene
Because eggshell membrane is a natural material derived from food-processing by-products, raw material quality control is extremely important. Eggshells are usually disinfected and washed with sodium hypochlorite and similar agents in food-processing facilities, so the risk of Salmonella contamination is very low. However, hygiene standards may vary among suppliers. It is essential to choose food-grade materials with appropriate safety documentation, such as GRAS status for human use.
Methods for separating eggshell membrane also vary, from chemical processing to mechanical separation, so it is preferable to select suppliers using manufacturing methods that minimize the risk of residual chemicals and contamination with impurities. Eggshell membrane is hygroscopic and can be susceptible to mold contamination, so proper moisture control and storage under low-humidity, cool conditions are necessary for powders. When commercializing products, adequate stability testing should be conducted to ensure that no quality deterioration or microbial growth occurs during the product’s shelf life, including consideration of whether preservatives are necessary.
With these points properly addressed, eggshell membrane can be used with confidence as a low-risk, safe ingredient. Compared with other joint-support ingredients, it tends to have milder side effects and a high tolerance for overconsumption, making it easier for pet owners to accept. Even so, its strong safety profile should not lead to complacency. Routine quality testing for each raw-material lot—especially microbiological and allergen testing—is directly linked to product reliability.
Comparison With Other Animal-Derived Supplement Ingredients
Eggshell membrane is often compared with other animal-derived joint-support ingredients such as glucosamine and chondroitin sulfate. These have traditionally been included in joint supplements and are typically derived from shellfish shells (glucosamine) or bovine and shark cartilage (chondroitin). The similarities, differences, and points to consider in combined use are outlined below.
The most important difference is that eggshell membrane is a multi-component ingredient, whereas glucosamine and chondroitin are single compounds. A single eggshell membrane ingredient can provide collagen, GAGs, amino acids, and more, whereas glucosamine alone plays a more limited role as a precursor for cartilage matrix sugars, and chondroitin alone mainly contributes to cartilage hydration and inhibition of degradative enzymes. For this reason, traditional product design has often relied on combining glucosamine and chondroitin to achieve synergistic effects.
Eggshell membrane is unique in that it inherently offers both glucosamine-like and chondroitin-like functions. In fact, it has been suggested that supplements containing eggshell membrane may produce better results than conventional glucosamine-plus-chondroitin products.
There also appear to be differences in speed of onset. Glucosamine and chondroitin generally require four to six weeks of administration—the so-called loading period—before effects become noticeable. By contrast, eggshell membrane often shows improvements in pain and mobility within one to two weeks, giving it an advantage in terms of faster action. This is thought to be due to the rapid anti-inflammatory effects of components contained in eggshell membrane, and it suggests potential use not only in chronic management but also in postoperative or post-injury acute-phase care.
In terms of safety, glucosamine and chondroitin are also generally safe ingredients, but glucosamine has occasionally been reported to cause soft stools or loss of appetite, especially at high doses. Chondroitin has a high molecular weight and relatively low absorption, so unabsorbed portions may remain in the digestive tract and contribute to soft stools at high intakes.
With eggshell membrane, such digestive issues are thought to be less likely because the required dosage is relatively small. From the standpoint of source-related allergies, glucosamine requires caution in cases of shellfish allergy, although fermentation-derived versions made from corn are now available. Chondroitin from bovine sources is less likely to trigger allergy, though reactions to gelatinous components are theoretically possible. Eggshell membrane, meanwhile, is comparatively low-risk as long as egg allergy is not an issue.
As for combined use, there appears to be no fundamental problem with using eggshell membrane alongside glucosamine and chondroitin. On the contrary, because their mechanisms may complement one another, combined use could potentially enhance joint-protective effects. Some commercial joint supplements already combine eggshell membrane with glucosamine, MSM, or other ingredients. However, because some effects overlap, total dosage should still be monitored when combining them.
For example, 500 mg of eggshell membrane contains only a few milligrams of glucosamine at most, since glucosamine makes up less than 1% of the ingredient. But if a full-dose glucosamine supplement is used at the same time, the total intake may become unnecessarily high. This is unlikely to create a serious toxicity problem, since excess glucosamine itself has low toxicity, but it may simply be economically inefficient.
Another notable animal-derived ingredient is undenatured type II collagen (UC-II), derived from chicken sternum cartilage. UC-II is thought to suppress joint inflammation by inducing oral immune tolerance at very low doses—often only a few dozen milligrams for dogs—but its mechanism is unusual and its effects are said to vary considerably among individuals.
Eggshell membrane, in contrast, acts more directly through nutritional support and anti-inflammatory effects, which may make its benefits easier to perceive. Green-lipped mussel (from New Zealand) is also used for joint support, with omega-3 fatty acids and GAGs as its principal components. Combining it with eggshell membrane may offer synergistic benefits. A comprehensive joint-support formula including eggshell membrane, green-lipped mussel, glucosamine, and chondroitin is theoretically promising.
That said, adding too many ingredients can make it unclear which component is responsible for the effect and can also drive up cost. Now that eggshell membrane alone is beginning to demonstrate meaningful efficacy, formulations centered on eggshell membrane with reduced levels of glucosamine and similar ingredients may offer product differentiation and improved palatability, since glucosamine can have a bitter taste.
Finally, eggshell membrane may pair well with omega-3 fatty acids and antioxidants such as vitamin E. EPA and DHA are useful for managing joint inflammation, and combining them with eggshell membrane may further enhance anti-inflammatory effects and help relieve joint pain. In fact, a comprehensive supplement containing eggshell membrane, omega-3s, Boswellia, and astaxanthin has already shown efficacy in dogs. On the other hand, when combined with high-calcium supplements, some attention should still be paid to total calcium intake, even though eggshell membrane itself contains only very small amounts of calcium.
Comparison Table of Joint-Support Ingredients
| Ingredient (Source) | Main Active Components / Actions | Evidence and Effects | Precautions / Risks |
|---|---|---|---|
| Eggshell membrane (inner membrane of chicken eggshell) | Collagen, chondroitin sulfate, hyaluronic acid, glucosamine, amino acids. Broad range of cartilage-building compounds with anti-inflammatory and chondroprotective effects. | In dogs, improvement in pain and function has been reported within 1 week. With 6 weeks of continued use, improved QOL and reduced cartilage breakdown markers have been observed. Rapid onset and strong safety profile are key advantages. | Contraindicated in dogs with egg allergy. Safety has been confirmed even at high doses. Raw eggshell membrane is poorly digestible, so enzymatically processed forms should be used. Quality control (sterilization, removal of foreign matter) is important. |
| Glucosamine (from shrimp/crab shells, etc.) | An amino sugar that serves as a precursor for glycosaminoglycans. Supports synthesis of cartilage matrix (proteoglycans) and helps reduce joint wear while supporting repair. | In dogs, improvements are more commonly reported when used together with chondroitin rather than alone. Effects usually appear gradually over 4–6 weeks. | Generally safe, but may rarely cause soft stools or digestive symptoms. Shellfish-derived forms require caution in animals with shellfish allergy. Considered safe even in diabetic dogs, but excessive intake should still be avoided. |
| Chondroitin sulfate (from bovine or shark cartilage) | A mucopolysaccharide that contributes to cartilage elasticity and water retention and may inhibit cartilage-degrading enzymes. Anti-inflammatory effects have also been suggested. | Clear evidence for efficacy as a single ingredient is limited. Some reports suggest pain relief when combined with glucosamine. Effects usually emerge over several weeks. | Absorption is relatively low, so only part of a large dose is absorbed. Unabsorbed material may remain in the digestive tract and contribute to soft stools. Purity varies by product quality; high-quality sources tend to be more expensive. |
In addition to the above, there are other joint-support ingredients such as MSM (methylsulfonylmethane), undenatured type II collagen, and green-lipped mussel extract. Because these differ in mechanism from eggshell membrane, a strategy of combining them for comprehensive joint support is also possible.
Since eggshell membrane can partially cover the roles of glucosamine and chondroitin on its own, formulation strategies can reduce the use of these conventional ingredients while still aiming for synergistic effects. No specific contraindications or interactions have been reported for such combinations, but as noted earlier, total intake of overlapping components should still be monitored.
Conclusion
Eggshell membrane is emerging as a promising functional ingredient in dog food and supplements, with scientific evidence increasingly supporting both its usefulness and safety. Its major components—collagen and glycosaminoglycans—help protect and repair joint cartilage, while its anti-inflammatory effects may rapidly reduce pain. This makes it highly attractive for product developers.
Clinical studies have already shown short-term improvements in joint symptoms, and eggshell membrane may offer advantages over traditional glucosamine and chondroitin products in terms of both speed of action and multifunctionality. From a safety perspective, eggshell membrane has a high tolerance margin, a low incidence of side effects, and has been shown to be suitable for long-term use.
Its one major precaution is egg allergy. As long as labeling and raw material control are handled properly, it can be considered an ingredient that consumers can trust.
In addition, eggshell membrane may offer secondary benefits such as support for skin and coat health and broader anti-aging effects, adding further value to joint-care products. A concept such as “dog food or supplements with eggshell membrane to support both joints and skin” could have strong appeal.
In product development, the key considerations are how much eggshell membrane to include and how to balance it with other ingredients. Based on previous research, continuous administration of eggshell membrane peptides at a level of several milligrams per kilogram of body weight appears likely to be effective in dogs.
Palatability should also be considered, and any characteristic eggshell membrane flavor may be masked with other flavoring agents if necessary. Eggshell membrane itself does not have a particularly strong off-note, but it should still be considered as part of overall flavor design.
Finally, it is worth noting that eggshell membrane is relatively favorable in terms of supply stability and cost. Because it is a by-product of egg processing, it can be supplied in large quantities, and its cost is trending downward as the market expands. As research continues, new benefits and mechanisms of action may be identified. In modern pet food development, where evidence-based ingredient selection is increasingly important, eggshell membrane can truly be described as one of the natural ingredients supported by science.