There is no strong scientific evidence to support the claim that oregano oil works for warts.
Oregano oil has received attention as possessing a variety of healing benefits including its use as a treatment for common ailments such as sinusitis, rosacea, and warts. Unfortunately, there is currently no strong supporting evidence from the medical research community to support these claims.
According to James T. Li, Mayo Clinic's asthma and allergy specialist, oregano, like other herbs, does have antifungal and antibacterial properties making it at least plausible that it can help to fight symptoms caused by bacteria and fungi.
Oregano Oil Warts Research
Recent research has indicated that an active constituent of oil of oregano called carvacrol may support the immune system.
A handful of studies have set out to explore the general antifungal, antibacterial properties of oil of oregano and have proven promising. A study in the journal Phytotherapy Research demonstrated the oils effectiveness against inhibiting parasites of the intestines, while a similar study published in the Pakistan Journal of Pharmaceutical Sciences demonstrated the oil's effectiveness against bacteria.
Force, M, WS Sparks , and RA Ronzio . "Inhibition of Enteric Parasites by Emulsified Oil of Oregano in Vivo." Phytotherapy Research 14.3 (2000): 213-214. Print.
Saeed, S, and P. Tariq. "Antibacterial Activity of Oregano (Origanum vulgare Linn.) against Gram Positive Bacteria." Pakistan Journal of Pharmaceutical Sciences 22.4 (2009): 421-424. Print.
There are currently no research studies published in peer accepted medical journals that have studied the effectiveness of oregano oil on warts.
Using Oil of Oregano on Warts
The book "Common Sense Pediatrics: Combining Alternative and Traditional Medicine in Everyday Practice" by S. Cornelia Franz MD, touts oil of oregano as an effective wart treatment and suggests rubbing a drop of oregano oil on a wart twice daily and it should disappear within a few weeks. Before experimenting with any alternative treatment, it's always best to consult your personal physician.