MSM and Quercetin:
Sulfur, Mast Cell Stabilization and Senolysis Explained
Methylsulfonylmethane (MSM) provides bioavailable sulfur for joints, cartilage, and connective tissue. Quercetin stabilizes mast cells, inhibits histamine, and acts as a senolytic flavonoid. Together they form a unique combination for joints, inflammation, allergies and healthy aging in dogs, cats and humans.
By Stefan Veenstra DVM
MSM: bioavailable sulphur as a structural building block
Methylsulfonylmethane (MSM) is an organic sulfur-containing molecule that occurs naturally in small amounts in vegetables, fruits, and meat. As a supplement, it provides bioavailable sulfur, an element essential for the structure of cartilage, tendons, ligaments, skin and hair. Sulfur is the third most abundant mineral in the body and a primary building block for collagen, glucosamine, and chondroitin.
MSM has a low molecular weight and high bioavailability: it is quickly and completely absorbed from the gut and crosses cell walls effortlessly, including the blood-brain barrier. Studies show that MSM accumulates rapidly in all tissues after oral ingestion, particularly in joints, liver, and brain.
Mechanisms of action of MSM
Sulfur supply for collagen and cartilage
Type II collagen, the primary structural protein of articular cartilage, requires sulfur bonds (disulfide bridges) for its three-dimensional stability. MSM provides the sulfate needed for the synthesis of glycosaminoglycans, the building blocks of cartilage matrix. In sulphur deficiency, which occurs relatively frequently in older or chronically ill animals, cartilage quality decreases.
NF-kB inhibition and ignition modulation
MSM inhibits the activation of NF-kB, the central transcription factor of pro-inflammatory cytokine production, and thus reduces the production of TNF-alpha, IL-1 beta and IL-6. A 2023 study in the Canadian Journal of Animal Science showed that MSM protects the barrier function of intestinal epithelial cells from LPS-induced damage, similar to the mechanisms that are also relevant at the gut barrier.
Study · J Orthop Res 2024 · MSM for osteoarthritis ankle
A comparative study showed that MSM supplementation in ankle osteoarthritis provided similar effects as methylprednisolone or hyaluronic acid on pain scores and joint function, without the side effects of corticosteroids. A relevant reference point for the clinical potential of MSM in joint complaints in humans and animals.
Glutathione synthesis and liver protection
MSM provides sulfur as a cofactor for glutathione synthesis. Mice studies show that MSM intake significantly increases liver glutathinone levels and protects against carbon tetrachloride-induced liver damage. This mechanism makes MSM relevant in liver burden, chronic disease and detoxification.
Quercetin: mast cell stabilizer, antihistamine and senolytic
Quercetin is a bioflavonoid found naturally in onions, apples, berries, and green tea. It is one of the most researched plant polyphenols, with a broad action profile that combines three clinically relevant mechanisms: mast cell stabilization, NF-kB inhibition, and senolysis.
Mast cell stabilization: the natural antihistamine
Mast cells are the central initiators of the allergic response. Upon contact with allergens, they degranulate and release histamine, leukotrienes, and prostaglandins, leading to itching, swelling, redness, and bronchoconstruction. Quercetin inhibits calcium influx into mast cells, a critical step in the degranulation process, reducing histamine release without destroying the mast cell.
This mechanism has earned quercetin the nickname “the natural Benadryl”. The difference with pharmacological antihistamines is fundamental: quercetin inhibits the source of histamine (the mast cell degranulation), while antihistamines block the histamine receptor after histamine has already been released. Quercetin therefore works preventively, antihistamines reactively.
Review · Biomedicine & Pharmacotherapy 2019 · Manure cell modulation
Theoharides et al. described in a comprehensive review the mechanisms by which quercetin stabilizes mast cells via calcium channel blockade and inhibition of PI3 kinase. The researchers concluded that quercetin has clinically relevant mast cell stabilizing effects in allergic and inflammatory conditions, similar to cromoglycate but via a plant polyphenol.
Senolysis: cleaning up senescent cells
One of the most recent and fascinating uses of quercetin is as a senolytic: a substance that selectively removes senescent cells. Senescent cells, also known as “zombie cells,” are cells that have stopped dividing but have not been cleaned up. They secrete a cocktail of pro-inflammatory compounds (the SASP: Senescence-Associated Secretory Phenotype) that damage surrounding healthy cells and contribute to aging, chronic inflammation, and degeneration.
Quercetin induces apoptosis (programmed cell death) in senescent cells via activation of pro-apoptotic signaling pathways, while healthy cells are less sensitive to this effect. Combinations of quercetin with dasatinib have been most studied in mouse studies as a senolytic regimen, but quercetin alone has also demonstrated senolytic activity in both in-vitro and in-vivo models.
Veterinary context · La Petite Labs review 2024 · Senolysis in animals
A recent veterinary review highlighted the increasing interest in senolytic strategies in older dogs and cats. Quercetin was discussed as the most accessible and safe option, with the caveat that senolysis is context- and dose-dependent and requires veterinary guidance in elderly or medication-taking animals.
Synergy of MSM and quercetin
MSM and quercetin are mechanistically complementary and mutually reinforcing on multiple levels:
MSM provides sulfur for collagen and cartilage matrix. Quercetin inhibits NF-kB and reduces inflammation that breaks down cartilage. Together: building and protecting joint cartilage at the same time.
Quercetin stabilizes mast cells and inhibits histamine. MSM supports the skin barrier via sulfur supply for keratin and collagen. Together: less allergic reaction and better skin structure.
Quercetin removes senescent cells via senolysis. MSM provides sulfur for glutathione synthesis and cellular maintenance. Together: active cell rejuvenation and antioxidant protection.
MSM increases liver glutathione and protects liver damage. Quercetin inhibits NF-kB-mediated liver inflammation. Together: protection of the liver via two complementary routes.
Relevance for dogs and cats
VCA Animal Hospitals describes MSM as a veterinary supplement used primarily in arthritis and as an antioxidant in dogs, and also in cats. The mechanisms of action of MSM, NF-kB inhibition, sulfur delivery and glutathione support, are not species-specific and are identical in carnivores.
Quercetin is widely used by integrative veterinarians as a natural antihistamine for seasonal allergies, environmental sensitivity, and itching due to mast cell tumors in dogs. The mast cell biology in dogs is similar to that in humans, making the mechanism directly translatable.
The combination of MSM and quercetin in one formula is particularly relevant in dogs and cats with concomitant joint complaints and allergic skin complaints, a combination that often occurs together in practice. Older animals with osteoarthritis often also have higher mast cell activity and therefore more allergic sensitivity.
In dogs with joint complaints as well as skin problems or seasonal allergies, the combination of MSM and quercetin mechanistically makes a lot of sense: MSM tackles the structural side of the joint problem, quercetin the inflammatory and allergic component at the same time. This reduces the need for separate supplements for each of these issues.
Interactions, side effects and contraindications
side effectsAt high doses, mild gastrointestinal complaints. Rarely skin reactions. MSM is one of the safest studied supplements in dogs and humans. In cats, caution at very high doses.
At high doses, mild gastrointestinal complaints. In case of long-term high doses, theoretical risk of renal strain: in case of renal insufficiency, caution. Do not combine with cyclosporine without veterinary consultation.
Quercetin may enhance the action of blood thinners (warfarin): monitoring recommended. MSM slightly potentiates the efficacy of NSAIDs: with combination, dose NSAIDs may be adjusted. Quercetin increases cyclosporine bioavailability: do not combine without veterinary consultation.
Renal insufficiency: lower dosages of quercetin, monitoring recommended. Pregnancy and lactation: insufficient safety data for quercetin. Immunosuppressive therapy: quercetin modulates the immune system, always in consultation with veterinarian.
Synergy with other supplements and protocols
Joint Protocol: Supplement to MSM/Quercetin as a Base Layer
MSM/Quercetin Complex works in a complementary way to Mobility Support and PEA Complex in the Joint Protocol. MSM provides the building blocks for cartilage, Mobility Support provides the complete cartilage matrix including growth factors, PEA modulates pain signaling. Quercetin adds mast cell stabilization and antihistamine action, relevant in dogs where joint complaints are associated with allergic sensitivity.
Skin protocol: quercetin as an antihistamine component
For allergic skin complaints, quercetin is the most direct plant mast cell stabilizer available. In the Skin Protocol, MSM/Quercetin Complex complements treatment via the histamine route, while PEA Complex via PPAR-alpha and Calanus oil via COX targets other inflammatory pathways. Together broad-spectrum allergy and inflammation modulation.
Aging protocol: quercetin as a senolytic component
In the Old Age Protocol, quercetin is the senolytic component: it helps clean up senescent cells that otherwise drive chronic inflammation (inflammaging). MSM simultaneously supports glutathione synthesis and structural tissue repair capacity. Both mechanisms are relevant in healthy aging in dogs, cats and humans.
NGD Care Joint Protocol: Structural Building Block and Inflammation Modulation
NGD Care Skin Protocol: Mast Cell Stabilization and Antihistamine Support
NGD Care Aging Protocol: Senolytic Component in Healthy Aging
Conclusion
MSM and quercetin are mechanistically complementary substances that together have a broader effect than each individually. MSM provides bioavailable sulfur for cartilage, connective tissue, and glutathione synthesis, and modulates NF-kB-mediated inflammation. Quercetin stabilizes mast cells for allergy control, inhibits NF-kB via an additional route, and clears senolysis senescent cells that drive inflammation.
The combination is particularly relevant in dogs and cats with concomitant joint complaints and allergic skin problems, a clinically common combination. When used in animals with kidney problems or immunosuppressive therapy, always consult a veterinarian.
View MSM/Quercetin Complex in the NGD Care webshop
Literature
- Jiao Y, Li H, Ren T, Kim IH. Protective effects of methylsulfonylmethane (MSM) on barrier function injury of porcine intestinal epithelial cells induced by LPS. Can J Anim Sci. 2023; 103(3):262–272.
- Van der Merwe M, Bloomer RJ. The influence of methylsulfonylmethane on inflammation-associated cytokine release before and following strenuous exercise. J Sports Med. 2016;2016:7498359.
- Joung YH, Darvin P, Kang DY, et al. Methylsulfonylmethane inhibits RANKL-induced osteoclastogenesis in BMMs by suppressing NF-kB. PLoS One. 2016; 11(7):E0159891.
- Theoharides TC, Conti P, Economu M. Impact of polyphenols on mast cells with special emphasis on the effect of quercetin and luteolin. Biomed Pharmacother. 2019;114:108824.
- VCA Animal Hospitals. Methylsulfonylmethane (MSM): veterinary reference. vcahospitals.com/know-your-pet/msm.
- Bonza.dog. MSM (methylsulfonylmethane) for dogs: joint mobility and inflammation support. 2026. bonza.dog/2026/02/msm-methylsulfonylmethane-for-dogs-joint-mobility-support.
- La Petite Labs. Senolytics in pets: quercetin, fisetin and senescent cells. lapetitelabs.com. 2024.
This information is educational in nature and based on available scientific literature. The studies mentioned are not always directly veterinary or specific to the formulation described here. This text does not replace a veterinary consultation and does not contain any therapeutic claims.