New allergies and intolerances

The development of new sensitivities or the development of new allergies and intolerances which were not present before the illness or allergies or intolerances that 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
 * allergies which can cause anaphylatic shock

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.