Allantoin and Comfrey (Symphytum officinale)
Comfrey is approved by the Commission E to treat blunt injuries due to the activity of triterpene saponins, tannins, and silicic acid as well as allantoin (3).
Allantoin has been extracted from the comfrey root and leaves but is now commercially manufactured. Allantoin is an antipholgistic, antioxidant, and soothing keratolytic that has antitrichomonal effect and induces cell proliferation. It is listed in the FDA over-the-counter monograph as a safe and effective skin protectant at 0.1% to 2.0% (15). Allantoin – and/or comfrey-based products are used to treat wounds, ulcers, burns, dermatitis, psoriasis, impetigo, and acne. When formulated with surfactant and benzalkonium chloride it is an effective hand sanitizer and onychomycosis therapy (3).
Comfrey contains hepatotoxic pyrriolizidine alkaloids which have resulted in deaths with oral consumption. It is carcinogenic and contraindicated in pregnancy and lactation (3).
Allantoin formulated with onion (Allium cepa) extract in a proprietary topical formulation improved the signs and symptoms of scars and keloids (16,17). No photoaging clinical trials using topical allantoin and/or comfrey have been published.