Development of new sensitivities

The development of new sensitivities or the development of allergies and intolerances which were not present before the illness or have worsened since is a common occurrence in ME/CFS. Early studies of Long COVID found that some patients developed new allergies including anaphylaxis, and worsening of existing allergies was also found.

Symptom recognition

 * The International Consensus Criteria lists sensitivities to food, medications, odors or chemicals as an optional criteria for diagnosis, under the section C. Immune, gastro-intestinal and genitourinary impairments.
 * 2018, The Centers for Disease Control and Prevention note ME/CFS patients can have "allergies and sensitivities to foods, odors, chemicals, or noise."

Types of sensitivities

 * Chemical sensitivities
 * Food sensitivities
 * Medicine sensitivities
 * Odor sensitivities

Prevalence

 * In a 2001 Belgian study, 48.5% of patients meeting the Fukuda criteria and 54.8% of patients meeting the Holmes criteria, in a cohort of 2073 CFS patients, reported new sensitivities to food or drugs.