Wound healing effects of a Symphytum herb extract cream (Symphytum x uplandicum NYMAN: ): results of a randomized, controlled double-blind study. From linear regression time to complete healing was determined to be 2.97 days faster with verum than with the reference (4.08 vs. 7.05 days). Barna M, Kucera A, Hladícova M, Kucera M, Wien Med Wochenschr. 2007; 157(21-22):569-74.

Randomized double-blind study: wound-healing effects of a Symphytum herb extract cream (Symphytum×uplandicum Nyman) in children. Barna M, Kucera A, Hladíkova M, Kucera M.
Arzneimittelforschung. 2012 Jun;62(6):285-9. doi: 10.1055/s-0032-1308981. Epub 2012 Apr 27.
PMID: 22549241 Clinical Trial.

Efficacy and safety of topically applied Symphytum herb extract cream in the treatment of ankle distortion: results of a randomized controlled clinical double blind study. Kucera M, Barna M, Horácek O, Kováriková J, Kucera A.
Wien Med Wochenschr. 2004 Nov;154(21-22):498-507. doi: 10.1007/s10354-004-0114-8.
PMID: 15638067 Clinical Trial.

Topical symphytum herb concentrate cream against myalgia: a randomized controlled double-blind clinical study. Kucera M, Barna M, Horàcek O, Kàlal J, Kucera A, Hladìkova M.
Adv Ther. 2005 Nov-Dec;22(6):681-92. doi: 10.1007/BF02849961.
PMID: 16510384 Clinical Trial.

Comfrey root: from tradition to modern clinical trials. Staiger C.Wien Med Wochenschr. 2013 Feb;163(3-4):58-64. doi: 10.1007/s10354-012-0162-4. Epub 2012 Dec 7.
PMID: 23224633.

Effect of a blend of comfrey root extract (Symphytum officinale L.) and tannic acid creams in the treatment of osteoarthritis of the knee: randomized, placebo-controlled, double-blind, multiclinical trials. Smith DB, Jacobson BH.
J Chiropr Med. 2011 Sep;10(3):147-56. doi: 10.1016/j.jcm.2011.01.003. Epub 2011 Jul 22.
PMID: 22014903

The Effect of Comfrey on Enoxaparin-Induced Bruise in Patients with Acute Coronary Syndrome: A Randomised Clinical Trial. Bagheri Z, Azizi A, Oshvandi K, Mohammadi Y, Larki-Harchegani A.
J Pharmacopuncture. 2021 Dec 31;24(4):196-205. doi: 10.3831/KPI.2021.24.4.196.
PMID: 35028171

[Efficacy and safety of symphytum herb extract cream in the treatment of pressure ulcers]. Stepán J, Ehrlichova J, Hladikova M.
Z Gerontol Geriatr. 2014 Apr;47(3):228-35. doi: 10.1007/s00391-013-0522-8.
PMID: 24048776 Clinical Trial. German.

Tolerability and effectiveness of an antitrauma cream with comfrey herb extract in pediatric use with application on intact and on broken skin. Kucera A, Barna M, Holcova S, Horacek O, Hladiková M, Ottillinger B.
Int J Pediatr Adolesc Med. 2018 Dec;5(4):135-141. doi: 10.1016/j.ijpam.2018.11.002. Epub 2018 Dec 13.
PMID: 30805549

Comfrey root: from tradition to modern clinical trials.

Staiger C.

Wien Med Wochenschr. 2013 Feb;163(3-4):58-64. doi: 10.1007/s10354-012-0162-4. Epub 2012 Dec 7.

PMID: 23224633

Comfrey: a clinical overview. Staiger C.
Phytother Res. 2012 Oct;26(10):1441-8. doi: 10.1002/ptr.4612. Epub 2012 Feb 23.
PMID: 22359388

Efficacy of a comfrey root extract ointment in comparison to a diclofenac gel in the treatment of ankle distortions: results of an observer-blind, randomized, multicenter study. Predel HG, Giannetti B, Koll R, Bulitta M, Staiger C.
Phytomedicine. 2005 Nov;12(10):707-14. doi: 10.1016/j.phymed.2005.06.001.
PMID: 16323288 Clinical Trial.

Efficacy and tolerance of a comfrey root extract (Extr. Rad. Symphyti) in the treatment of ankle distorsions: results of a multicenter, randomized, placebo-controlled, double-blind study. Koll R, Buhr M, Dieter R, Pabst H, Predel HG, Petrowicz O, Giannetti B, Klingenburg S, Staiger C.
Phytomedicine. 2004 Sep;11(6):470-7. doi: 10.1016/j.phymed.2004.02.001.
PMID: 15500257 Clinical Trial.

Comfrey extract ointment in comparison to diclofenac gel in the treatment of acute unilateral ankle sprains (distortions). D'Anchise R, Bulitta M, Giannetti B.Arzneimittelforschung. 2007;57(11):712-6. doi: 10.1055/s-0031-1296672.
PMID: 18193693 Clinical Trial.

A critical scoping review of external uses of comfrey (Symphytum spp.). Frost R, MacPherson H, O'Meara S.
Complement Ther Med. 2013 Dec;21(6):724-45. doi: 10.1016/j.ctim.2013.09.009. Epub 2013 Oct 8.
PMID: 24280482