Comfrey leafs grow in Europe and Western Asia and play a large part in gardening. They are also used as a herbal remedy that is believed to help remove phlegm from the lungs, as well as to provide various other therapeutic benefits. However while some of these treatments are debated, what is known is that eating comfrey can lead to liver toxicity. It contains dangerous levels of hepatotoxic pyrrolizidine alkaloids and scientists agree it should never be ingested. However used externally it may be more useful.
Comfrey oil is commonly used as a skin treatment on its own and as an ingredient in many other products. This is believed to help to stimulate the growth of healthy skin cells while also helping to avoid inflammation. Thus it is theoretically useful for treating sprains and other minor injuries. Used topically it should not be toxic, and its allantoin content may well mean that it is helpful in this touted benefit. However it is unlikely that it could reach deep enough to affect problems such as sprains and breaks other than to reduce inflammation – which can be achieved more definitively with other products.
It may also for this reason be effective as a potential anti-ageing cream which could help to smooth the skin by encouraging the production of new skin cells. It’s worth noting however that studies have found that even the most expensive and effective skin creams only achieve around a 10% reduction in wrinkles maximum. Allantoin is also frequently present in shampoos, lipsticks, anti-acne products and many skin creams, and may help make them somewhat effective – just don’t hope for a miracle.
In short, if you have been injured then topical use of comfrey oil may help and won’t be damaging, though other products will likely prove more effective. Likewise products containing allantoin might help to improve the appearance of skin damage, but just don’t expect wonders. And certainly do not eat it…