Milk thistle (aka silymarin) is a dietary supplement traditionally used by herbalists to treat and to prevent damage to the liver. Milk thistle has been shown to be one of the safest of herbal preparations, and current and ongoing medical research is bearing out the efficacy of milk thistle in treating and preventing liver damage from alcohol and from other causes, although more tests of a high degree of rigor are called for.
A thorough review of the literature on milk thistle current to the year 2000 can be found online in the free full text US Government Publication Milk Thistle: Effects on Liver Disease and Cirrhosis and Clinical Adverse Effects which is located at http://www.ncbi.nlm.nih.gov/books/NBK33277/. This review finds that the evidence to date is strongly suggestive that milk thistle helps heal the liver, although studies to date are not yet conclusive.
A more recent review of the literature can be found in Saller (2008).
Since there are no prescription drugs available to reverse liver damage--milk thistle may be your only recourse.
Lawrence V, Jacobs B, Dennehy C, et al. (2000) Milk thistle: effects on liver disease and cirrhosis and clinical adverse effects. Evidence Report/Technology Assessment No. 21. AHRQ Publication No. 01-E025. Rockville, MD.
Pubmed Abstract: http://www.ncbi.nlm.nih.gov/pubmed/11262867
Free Full Text: http://www.ncbi.nlm.nih.gov/books/NBK33277/
Rainone F. (2005).Milk thistle. Am Fam Physician. 72(7), 1285-8.
Pubmed Abstract: http://www.ncbi.nlm.nih.gov/pubmed/16225032
Free Full Text: http://www.aafp.org/afp/2005/1001/p1285.html
Saller R, Brignoli R, Melzer J, Meier R. (2008). An updated systematic review with meta-analysis for the clinical evidence of silymarin. Forsch Komplementmed. 15(1), 9-20.
Pubmed Abstract: http://www.ncbi.nlm.nih.gov/pubmed/18334810
Tamayo C, Diamond S. (2007). Review of clinical trials evaluating safety and efficacy of milk thistle (Silybum marianum [L.] Gaertn.). Integr Cancer Ther. 6(2), 146-57.
Pubmed Abstract: http://www.ncbi.nlm.nih.gov/pubmed/17548793