Loratadine

Loratadine or Claritin is H1 receptor antagonist which is commonly used as a non-sedating anti-histamine. It is a potential treatment for mast cell activation syndrome (MCAS). Loratadine is sometimes misspelled as Loratidine.

MCAS and ME/CFS
The March 2 and 3, 2018, physicians summit in Salt Lake City, Utah addressed the potential role of MCAS treatment in ME/CFS treatment. Several physicians remarked on the relatively high prevalence of MCAS in their ME/CFS patients (making estimating of roughly half their patients) and its significance in pointing toward treatment of symptoms associated with ME/CFS. Dr. Susan Levine suggested that while MCAS likely only affects a subset of ME/CFS patients, for those it does, it can manifest as inability to tolerate certain foods or medications and "If we can reduce the mast cell problem, we can facilitate taking other drugs to treat ME/CFS."

Long COVID
Loratadine has limited evidence for use in Long COVID patients in a small observational study by Glynne et al. (2022).

Notable studies

 * 2022, Long COVID following mild SARS-CoV-2 infection: characteristic T cell alterations and response to antihistamines - (Full text)

Learn more

 * Medications to Treat Mast Cell Diseases - The Mast Cell Disease Society
 * Loratadine - drugs.com