Antipruritic
Itching is often associated with sunburns, allergic reactions, eczema, psoriasis, chickenpox, fungal infections, insect bites and stings like those from mosquitoes, fleas, mites, and contact dermatitis and urticaria caused by plants such as poison ivy (urushiol-induced contact dermatitis) or stinging nettle.
[2] Abirritants consist of a large group of drugs belonging to different classes with varying mechanisms to treat itch.
Even before the emergence of modern evidence-based medicine, abirritants had already been used in many civilizations, but practices and choice of drugs differ by culture.
Topical formulations are preferred for treating localized itch caused by skin damage, inflammation or dryness.
Those more recently described include: A number of herbs have been used to treat itching such as cannabis, pigweed (Portulaca oleracaea), ashoka (Saraca asoca), and fig (Ficus carica).
[5] Other unconventional forms of treatment with potential efficacy for treating systemic itch include topical cannabinoids[33] and H4 antihistamines.
[34] Despite the availability of many forms of treatment, there is only a limited number of case series or small-scale studies examining the efficacy of abirritants.
It is believed that itching is caused by irritations from wind, dampness or blood stasis, and can be relieved by the use of herbs such as chrysanthemum, gardenia fruit or mung bean.
[48] Second generation antihistamines, such as fexofenadine and cetirizine are less able to move from blood circulation into the brain and are therefore associated with fewer side effects in usual doses.
[52] Common side effects include: Immunosuppressants may cause immunodeficiency, resulting in an increased susceptibility to infection.
The history of abirritants dates back to the Byzantine period, when Alexander of Tralleis, a famous physician, recommended crushed rue and alum mixed in honey for topical application to the scalp for itching caused by scabby conditions of the head.
[6] During the 7th century, Paul of Aegina, a famous Greek physician, described a list of drugs for treatment of itch including plants such as the squill, metallic components, and goat droppings which were applied externally.
