This is an old drug with most of the studies in 1970-1990. It is very different in action from antihistamines (i.e. it is NOT an antihistamine) with an awesome safety record. A reader asked me to assemble and review the literature. Mast cell and histamine issues are often reported with other conditions; the domination of other symptoms may mask the mast cell issues.

Conditions Often Comorbid With Mast Cell Diseases

• Chronic inflammatory response syndrome (CIRS)

• Fibromyalgia syndrome (FMS)

• Ehlers-Danlos Syndrome (EDS)

• Gulf War Illness (GWI)

• Interstitial cystitis/bladder pain syndrome (IC/BPS)

• Irritable bowel syndrome (IBS)

• Kounis syndrome

• Multiple chemical sensitivity syndrome (MCSS)

• Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)

• Post-Lyme syndrome

• Postural orthostatic tachycardia syndrome (POTS)

• Post-traumatic stress disorder (PTSD)

Cromolyn sodium is a medication used to manage bronchial asthma, allergic rhinitis, and certain allergic eye conditions such as vernal conjunctivitis, keratitis, and keratoconjunctivitis. It is a mast cell stabilizer. 

Cromolyn Sodium – Continuing Education Activity – StatPearls [NIH site – 2022]

Notes from the above:

• Derived from Mediterranean herb called Ammi visnaga
• Cromolyn sodium metered spray is used to prevent and relieve nasal symptoms of hay fever and other nasal allergies like runny or itchy nose, sneezing, and allergic stuffy nose.[7]
• Cromolyn sodium is off-labeled used for preventing serious reactions to foods.[8]
• The effect of cromolyn sodium on mast cells lasts for approximately 6 hours
• Cromolyn sodium inhibits immediate and late reactions.[15][12] 
• Adverse reactions reported with the inhalation solution were throat irritation and hoarseness, esophagitis, laryngeal and pharyngeal edema, drowsiness, dizziness, bronchial irritation, pulmonary infiltrates, and cough.[19]
• Given its safety profile and current evidence, its use is likely most favorable for those who cannot tolerate intranasal corticosteroids or require short-term prevention before known exposures.^6,7 

I was unable to find any generic clinical studies for Cromolyn with Myalgic encephalomyelitis/chronic fatigue syndrome or ASD (despite mast cell issues being associated with inflammation of the brain.

Availability

In the US available at retail (Walmart etc) from several brand,

• NasalCrom Nasal Spray Allergy Symptom Controller, 200 Sprays, – $16.26 – i.e. 1 cent per spray
• HealthGuard Cromolyn Sodium Nasal Spray, 200 Sprays – $12.99

The Herb Ammi Visnaga (Visnaga daucoides )

Used for over 2000 years

• “it is used in modern medicine to treat many aliments such as renal colic and coronary insufficiency, and is used as an antioxidant, antifungal, and antibacterial, with a larvicidal effect on mosquito larvae…. A.K.A. Khella Baldi or toothpick weed, In Arabic countries A. visnaga has many common names such as Khella baladi, Khella, Khellah, Khellakl, Chellah, Kella, Gazar sheitani, Kammon habashi, Bizer Al-Khilla, Kulla, and Swak Al-Nabi. In Turkey, it is known as disotu, kilir, and hiltan.” [2020]

Headaches — likely a spray symptom

A study of this spray against a placebo was found “The most common adverse events in both groups were headache and rhinitis, and there was no significant difference in the rates of such events between groups.” [2002]. This suggests that the spraying is a more likely cause, not the cromolyn nasal spray.

Literature

• Ways to Address Perinatal Mast Cell Activation and Focal Brain Inflammation, including Response to SARS-CoV-2, in Autism Spectrum Disorder. [2021]
• Mast Cells, Stress, Fear and Autism Spectrum Disorder. [2019]

Bottom Line

Given its awesome safety record, I would suggest a discussion with your medical professional on doing a course of over-the-counter nasal spray (done before each meal and at bed time – because it effects lasts only 6 hours). A single bottle should last for 50 days.