Patients receiving menopausal care therapy reported atopic conditions and histamine-associated symptoms and attributed a variety of other symptoms to hormone therapy, according to findings presented at The Menopause Society 2026 Annual Meeting in San Diego.

“These findings support asking about atopic history, histamine intolerance, medication sensitivity, and symptom timing during menopause intake,” Maria G. Valdez, MD, a family physician at The Collaborative in Tualatin, Oregon, and her colleagues wrote.

“They also suggest that patients who report hormone sensitivity may need individualized estradiol titration, consistent with menopause guidance that hormone therapy should be individualized by formulation, dose, route, duration, timing, and patient-specific risk profile,” she said.

To better understand atopic and histamine-related symptoms in those receiving care for menopause, the researchers distributed surveys in their practice from April 29 to May 16, 2026, and analyzed the responses from 766 participants, including 79.9% reporting current hormone therapy use.

Half the participants (49.9%) reported recent skin changes, including dryness, itching, or breakouts. About a third of respondents (33.8%) reported having allergies, asthma, or eczema, and 5.7% reported histamine intolerance. A formal mast cell activation syndrome (MCAS) diagnosis was reported by 1.8% of participants.

The researchers focused on the symptoms reported by the 132 respondents (17%) who responded to questions about estradiol and histamine or mast cell reactions, 41.7% of whom said that changes in estradiol appeared to trigger histamine, allergic, or mast cell responses.

Among those 132 respondents, mood changes or anxiety were the most commonly reported symptoms they attributed to changes in estradiol (51.5%), followed closely by brain fog or difficulty concentrating (42.4%). A third (33.3%) reported experiencing itching without a visible rash, and just over a quarter (26.5%) reported palpitations or a racing heartbeat linked to changes in estradiol. About 1 in 5 respondents experienced flushing or sudden redness (22.7%) or diarrhea (18.9%).

Smaller proportions reported hives or welts (10.6%), shortness of breath or wheezing (9.1%), or nausea or vomiting (8.3%) as symptoms they believed were caused by changes in estradiol.

Among the 128 respondents who answered questions about the timing of their symptoms, only 10.9% reported symptoms occurred when they started hormone therapy or after a dose change, and 16.4% reported symptoms before menses. A more common response (38.3%) was no clear pattern to the symptoms’ timing.

The authors also reviewed 32 free-response comments that “identified recurring patient-described themes, including gradual estradiol titration, sensitivity to dose changes, new or worsening atopic symptoms during perimenopause, and antihistamine use by some respondents while continuing estradiol therapy.”

The authors called for research to prospectively evaluate possible associations between estradiol therapy and mast cell-associated symptoms in people receiving menopausal care. Mast cells express estrogen receptors, so it’s possible that estradiol influences mast cell activation and mediator release, the authors explained, though they said it’s important to interpret patient-reported symptoms cautiously because an MCAS diagnosis has other objective criteria beyond symptoms.

Kecia Gaither, MD, MPH, MBA, an ob/gyn and maternal fetal medicine physician and associate professor of clinical ob/gyn at Weill Cornell Medicine in New York City, was not involved in the research but agreed that it’s worth asking patients about atopic and histamine symptoms while they’re taking estradiol.

However, the data in this study only generate a hypothesis, she told Medscape Medical News, and can’t show cause and effect. Limitations of the study included using a convenience sample for the survey and the usual selection bias and recall bias that can occur with surveys. The use of self-reported data without confirmation of diagnosis and the lack of information on dose, route, or formulation of hormone therapy also limit how much it is possible to draw from the study, she said.

Gaither did note that the biology makes sense, referencing a 2026 research review that found menopause can worsen existing allergic disease or trigger new disease. That review also found that estrogen-dominant hormone therapy can worsen urticaria in susceptible women and that transdermal routes may be better tolerated.

“Clinicians should ask about atopic history but as part of a good intake, not as a way to screen people out of hormone therapy,” Gaither said. “For patients who report sensitivity to hormones, practical options include starting low and titrating slowly and considering route and timing of doses. Patients should be apprised that new itching or flushing doesn’t automatically mean they have to stop hormone therapy.”

Gaither noted that the most commonly reported symptoms — mood changes, anxiety, and brain fog — are not specific to histamine and heavily overlap with menopause itself. However, if patients experience hives, wheezing, or swelling, “refer to an allergist or immunologist rather than adjusting doses on your own,” she said.

No external funding was used for the research. Valdez and Gaither had no disclosures.

Tara Haelle has been an independent science/health journalist for over 15 years, with work appearing in over two dozen trade and consumer publications.