Local primary irritation is by far the most frequent cause of pruritus ani et vulvae. Other causes are contact dermatitis, specific dermatological diseases, disease of the anal, rectal, and genitourinary tracts, disease of other organs, and psychogenic disturbances. Etiological diagnosis is often difficult because pruritus from any cause can exist for only a short time before visible secondary changes are induced by scratching and medication. Anal pruritus scarcely exists in geographical areas where bathing with water and no soap or toilet paper is the custom after defecation. When an organ system other than the anogenital apparatus is involved, all local sources of irritation should be removed and conservative treatment applied until the true source of the itching sensation becomes apparent. Presumed psychogenic disturbances are made worse by treatment if the diagnosis happens to be incorrect, and the supposed emotional exhaustion rapidly disappears when the real etiology is discovered and eliminated. More time should be spent on searching out the underlying cause of anogenital pruritus. Specific sensitization to condiments should not be overlooked in unsolved cases.
Osborne ED, Stoll HL. PRURITUS ANI ET VULVAE. JAMA. 1959;169(2):124-127. doi:10.1001/jama.1959.03000190026007