Hi again- It was easier than I thought to got back in my messages and find the referrals my PCP sent me. This is a direct copy/paste from what she gave me:

Dr. Vivian Chou
HOME | Illinois Allergy & Asthma Specialists | Chicago Allergist (ilallergyasthma.com)
Affiliated with Advocate
Takes insurance
Locations in Chicago and Evanston

BILIMORIA, DR. YASMEEN
Glen Allergy and Asthma
2550 Compass Rd.
Unit K
Glenview, IL 60026
847.832.6000
847.832.1900 fax
https://www.northshore.org/apps/findadoctor/physicians/yasmeen-bilimoria
I’m told that Dr. Bilmoria is “the person” in the Chicago area for MCAS. My PCP and a physician on the Long COVID team (both at Northwestern Medicine downtown campus) typically refer to her for MCAS.

Dr. Chou, she doesn’t have direct experience with, but she told me she has a patient (she treats a lot of patients with various chronic pain conditions that cross over with things like MCAS) who’s MCAS significantly improved under her care.

Hope that helps.