MCAS and Endometriosis Pain - What Research Suggests So Far

The possible MCAS and endometriosis pain connection

MCAS and endometriosis may overlap through mast-cell activity that amplifies inflammation and nerve sensitivity. Mast cells inside and around lesions may help explain pain that exceeds what imaging suggests, persists after surgery, or flares with hormones or stress. Local mast-cell activity does not mean someone has systemic mast cell activation syndrome (MCAS), and neither condition has been shown to cause the other.

Some people also notice food- or allergy-related flares, IBS-type bowel symptoms, migraines, or dizziness and a fast heart rate resembling POTS. These patterns are worth discussing with your doctor, without assuming they all have one cause.

How immune activity can amplify pain

Mast cells are immune cells best known for allergic reactions, but they also live throughout the body, particularly near nerves and blood vessels. When activated, they release chemical messengers, called mediators, including histamine, tryptase, cytokines, and growth factors.

These substances can irritate pain-sensing nerve endings, called nociceptors, and make them more responsive. They can also promote nerve growth and tissue rewiring, sustain inflammation, and potentially contribute to lasting changes in how the spinal cord and brain process pain. That longer-term amplification is often called central sensitization.

Two 2025 reviews of human and experimental findings on endometriosis pain described a two-way immune-nerve loop: immune activation increases nerve sensitivity, and nerve activity can reinforce inflammation. Mast cells may act as an important connection between hormones, inflammation, nerves, and pain processing. This offers a plausible explanation for burning, stabbing, or radiating pain, pain that spreads beyond the pelvis, and pain that continues after lesions are treated.

Local activity and systemic MCAS are different

Activity within pelvic tissues

Mast-cell activation inside lesions and nearby pelvic tissues may amplify pelvic pain. This can occur without systemic MCAS. Endometriosis is primarily an abdominal-pelvic disease, although it certainly has body-wide effects.

The available tissue and experimental findings concern endometriosis. They cannot establish a link between MCAS and adenomyosis.

Systemic symptoms and possible overlap

MCAS is a systemic syndrome involving episodes of mast-cell mediator release that cause symptoms across multiple body systems. It remains an evolving diagnosis, and having endometriosis does not establish MCAS. Likewise, an MCAS diagnosis does not establish endometriosis.

In some people, local pelvic mast-cell activity may overlap with systemic mediator symptoms. That broader sensitivity may intensify flares, produce symptoms outside the pelvis, and lower pain thresholds. However, endometriosis has not been shown to cause MCAS, and MCAS has not been shown to cause endometriosis.

Evidence from lesions and nearby nerves

The two 2025 reviews of endometriosis pain described human tissue and animal findings in which mast cells were more numerous and more activated in lesions. Activated mast cells release the contents of their granules, a process called degranulation. These cells also tended to cluster near nerve fibers.

In a 2023 tissue and laboratory study involving women with ovarian endometriosis, investigators found increased mast-cell markers in lesions and identified mast cells carrying an estrogen receptor called GPR30. Mast-cell-related markers were higher in lesions from women reporting pain than in those reporting no pain. Mast cells were also more frequently positioned close to nerve structures in the pain group.

These findings suggest that pain may partly depend on the immune and nerve environment within a lesion, rather than simply its size or location. They do not establish mast cells as the sole cause of endometriosis pain.

Hormonal shifts may intensify nerve sensitivity

Many people notice worsening pain around ovulation or before a period, or changes after starting or stopping hormonal medication. Estrogen may influence pain by activating immune cells that directly sensitize nerves, in addition to its effects on lesion growth.

A 2025 review of human and experimental findings on estrogen-related endometriosis pain described mast-cell activation through estrogen receptors, including pathways outside the classical nuclear receptors. The proposed sequence is that estradiol, a form of estrogen, activates GPR30 on mast cells. The cells then release fibroblast growth factor 2, or FGF2, which can increase nerve growth and sensitivity.

In the cell experiments accompanying the 2023 ovarian-lesion study, estradiol increased FGF2 production in rodent mast cells through an internal signaling pathway called MEK/ERK. Secretions from those cells promoted the growth of nerve extensions and increased activation in nerve-like cells. In rats with experimentally induced endometriosis, inhibiting the FGF2 receptor, FGFR1, improved pain-like behaviors.

Rat models are not great models for endometriosis. This pathway is a concept to explore further in humans, not a ready-to-use FGF2-blocking treatment. It may help explain rapid pain flares with hormonal shifts or substantial pain despite a modest lesion burden.

Why pelvic pain can persist after excision

Sensitization after a trigger is reduced

Persistent pain after apparently good surgery must not be dismissed or automatically treated as proof that surgery failed. Endometriosis pain can involve neuroinflammation and altered signaling at several levels: pelvic tissues, nerves, dorsal root ganglia, the spinal cord, and the brain. The dorsal root ganglia are clusters of nerve cells that relay sensory signals toward the spinal cord.

A 2025 review of human and animal findings on endometriosis pain described inflammatory mediators in lesions and pelvic fluid, including TNF-alpha, interleukins, prostaglandins, nerve growth factor, and chemokines. These substances can stimulate and sensitize sensory nerves. The review also described greater nerve-fiber density near lesions, which may correlate with pain.

When nerves have been sensitized for months or years, they may continue to overreact after the original trigger is reduced. Central sensitization can also lower pain thresholds elsewhere, contributing to widespread pain or several painful sites. Stress hormones and autonomic activation can influence this heightened responsiveness, helping explain flares during stress or poor sleep.

Repeated mast-cell mediator release could, in theory, keep feeding that cycle and make pain harder to relieve with surgery alone. It is a possible contributor, not an established explanation for every person with persistent pelvic pain.

Anatomic and fibrotic effects on nerves

Structural causes also need consideration after excision. Unrecognized or inadequately addressed disease may directly compress nerves through its anatomic effects or through fibrosis, meaning scar-like tissue.

This falls within neuropelveology, the field concerned with pelvic nerve disorders. Persistent pain warrants attention to these structural possibilities as well as to nervous-system sensitization.

Flares and overlapping symptoms worth tracking

Bowel, bladder, migraine, and autonomic symptoms

Mast-cell mediators can make nerves serving internal organs more reactive, a process called visceral hypersensitivity. If pelvic nerves are already sensitized, bowel activity or bladder filling may be experienced as pain more readily. This can make it difficult to separate endometriosis-related pain from IBS-type symptoms or bladder pain.

Central sensitization and neuroinflammation are also relevant concepts in migraine, including associated head and neck symptoms. Mast-cell activity and autonomic dysfunction are frequently discussed together in clinical care for MCAS and POTS. However, the 2025 reviews of endometriosis mechanisms do not establish the specific pathways linking endometriosis-related mast-cell activity to IBS, migraine, or POTS.

Flushing, itching or hives, gastrointestinal changes, migraines, palpitations, and temperature intolerance are worth discussing with your clinician when they cluster with pelvic pain. A possible mediator pattern could affect decisions about triggers, flare plans, and supportive medications while standard endometriosis care continues.

Patterns that may point to a flare component

If mast-cell mediators and sensitization contribute to your pain, possible patterns include:

• Pain flares with hormonal shifts, including changes around ovulation or before a period.
• Stress-triggered flares that involve symptoms throughout the body, rather than only the pelvis.
• Increased sensitivity to pressure, sex, bowel movements, or bladder filling.
• Only partial improvement after lesion-directed treatment unless the nervous-system component is also addressed.

These patterns do not diagnose MCAS. They describe possible biological amplification involving immune, hormonal, and nerve signaling, often at the same time. Pain arising through those processes is real, not imagined.

Treatment ideas are not established endometriosis pain care

Antihistamines and mast-cell stabilizers

H1 and H2 antihistamines and mast-cell stabilizers are theoretically promising, particularly for pain that has resisted other treatment. However, endometriosis-specific clinical trial evidence is lacking. The two 2025 reviews of endometriosis pain mechanisms discuss mast-cell targeting as a potential direction, not an established treatment guideline.

Understanding this biology can help explain why pain persists and why non-hormonal treatment targets may matter. It does not justify self-treatment or unsupervised off-label medication use. With proper evaluation, some individual patients may benefit from lower-risk off-label medication under appropriate medical supervision.

JAK inhibitors and off-label risks

The JAK/STAT pathway is an internal signaling system involved in both inflammation and nerve growth. A 2025 review of human and experimental endometriosis findings proposed inhibiting this pathway as a future treatment direction. There is currently no direct evidence establishing that JAK inhibitors effectively treat endometriosis pain.

Tofacitinib is one such medication used for other inflammatory conditions, including rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis. Its use for this purpose is experimental and carries potentially severe risks. It cannot be advised without a full risk-benefit discussion and careful monitoring, and insurance does not cover experimental therapy for this purpose.

How to use these patterns at an appointment

Bring a symptom and trigger record

Track pelvic pain alongside symptoms such as flushing, itching or hives, bowel changes, migraines, and palpitations. Record cycle timing, stress, sleep, and diet as well.

The timing and clustering of symptoms can help guide evaluation. A clinician or endometriosis specialist familiar with current findings may help distinguish a possible mediator pattern from other causes and individualize the plan.

Ask about every possible pain driver

Your clinician can help separate lesion-related pain and fibrosis, pelvic floor or musculoskeletal contributors, and sensitization or mediator-driven flares. Useful questions include:

• Could lesions, fibrosis, or direct nerve compression still be contributing to my pain?
• Could pelvic floor or other musculoskeletal problems be adding to it?
• Does my symptom record suggest central sensitization or a possible mast-cell mediator pattern?
• If pain persists after surgery, what is the plan for addressing sensitization as well as any remaining disease?

That plan may include pelvic physical therapy when appropriate, neuromodulatory pain strategies that change how pain signals are processed, and targeted management of sleep and stress physiology. Care should consider these contributors rather than focusing only on repeated lesion treatment.

What remains unknown about individual responses

Questions research has not answered

Much of the work on mast cells and endometriosis consists of tissue studies, cell experiments, animal models, and reviews, rather than large clinical trials of mast-cell-targeted pain treatment. The 2023 GPR30-FGF2 experiments cannot yet identify which patients would benefit, what doses would be safe, or whether improvement would last for years.

Several patient-facing questions remain unanswered:

• Which symptom profiles predict a mast-cell-driven component of pain?
• Do certain lesion types, such as deep infiltrating disease, consistently show closer mast-cell and nerve proximity, and do they respond differently to treatment?
• How often is systemic MCAS present, compared with localized mast-cell activation in pelvic tissues?
• Which combination of treatments best prevents the cycle of inflammation, nerve sensitization, and central sensitization from becoming entrenched?

What the evidence can help with now

Endometriosis pain is not a measure of lesion presence or size. Evaluation may need to address lesions, fibrosis, other pelvic pain drivers, and nervous-system sensitization together to get the full picture. Mast-cell activity offers one possible explanation for pain that is persistent, flare-prone, or accompanied by whole-body symptoms.

Work on immune-nerve pathways may, and probably will, expand non-hormonal treatment options. Today, its practical value is in individualized evaluation and comprehensive pain care, including carefully supervised, lower-risk off-label treatment where appropriate. A knowledgeable endometriosis specialist can help assess which options fit a person’s symptoms and risks.