The active ingredients in antioruritics (including topical (applied directly to the body: creams, oinments, lotions and sprays) and oral drugs) usually belong to these classes:
Antihistamines such as diphenhydramine (Benadryl)
Corticosteroids such as hydrocortisone topical cream, see topical steroid
Counterirritants, such as mint oil, menthol, or camphor
Local anesthetics such as lidocaine and benzocaine topical creams
Nalfurafine, an orally-administered, centrally-acting κ-opioid receptor agonist approved for uremic pruritus and effective in animal models of other prurituses
See also related entries in Aurametrix such as anal itching or itchy eyes