Herbs with a drying, tightening effect on tissues are referred to as astringents. In animals, astringent herbs are primarily used to promote wound healing and resolve diarrhoea. Astringent comes from the Latin adstringere, meaning ‘to bind fast’ and astringent herbs generally exert this effect due to the presence of tannins.
The English idiom ‘to pucker up’ refers to the wrinkling of the lips as they pull together in preparation for a kiss. In herbal medicine, plants rich in tannins are used to tighten and pull together tissues. This sensation will be familiar to red wine or tea drinkers, as both drinks are rich in tannins. Eating an unripe banana produces a similar effect. Tannins are plant chemicals that bind proteins. The mucous membranes of the mouth are tightened as proteins are cross-linked by tannins creating the puckered, dry feeling in the mouth.
Plants use tannins to deter herbivores from eating their leaves or bark. High tannin content causes a drying of the mouth and impairs protein digestion and absorption in animals. However, the effects of tannins can also be beneficial in certain circumstances, and so tannin containing plants are not entirely avoided by animals.
Tannins may have natural anthelmintic effects in animals, reducing intestinal worm burdens. Some animals, like sheep, goats and cattle, appear to carefully adjust their intake of tannin-containing plants so as to keep internal parasites under control; an example of self-medication behaviour in animals.
Common Herbal Astringents
Tannins are found in many plants, many of which have been used for wound healing and diarrhoea by humans and other animals for thousands of years. Here are some commonly used astringent herbs:
- Carpet geranium (Geranium incanum) – leaves of this indigenous geranium contain tannins and have been used as a tea substitute, to treat menstrual problems (hence the common name Vrouebossie), and to treat mild diarrhoea.
- Cinnamon (Cinnamomum verum) – this well-known warming, aromatic spice made from the dried inner bark is rich in tannins and antiseptic oils, making it a useful remedy for mild diarrhoea.
- Guava (Psidium guajava) – although not indigenous, guava trees are common in South Africa and the leaves, rich in tannins, have been used traditionally for diarrhoea.
- Oak (Quercus albus) – tannin-rich bark from oak or fir trees was used in the process of tanning animal hides to form leather. The word ‘tannin’ comes from tanna, the old High German name for the Fir tree (Tannenbaum) was also used for this purpose.
- Pomegranate (Punica granatum) – the rind of the pomegranate fruit (granaatskille in Afrikaans) is an old Cape remedy for diarrhoea, and the bark was used as a tapeworm remedy.
- Sour Fig (Carpobrotus edulis) – juice from this indigenous succulent is tannin-rich and antiseptic, and provides a useful first-aid remedy for minor wounds and digestive upsets in animals.
- Sweet Thorn (Acacia karroo) – bark from this common indigenous tree was used historically for tanning leather. The leaves and bark have been used traditionally as a diarrhoea remedy, and the source of the extract is known as ‘black catechu’.
- Witch hazel (Hamamelis virginiana) – a well-known North American astringent, often used in cosmetic preparations and useful topically in animals for wound healing.
- Yarrow (Achillea millefolium) – yarrow leaves have astringent, styptic and antiseptic effects making it ideal for minor wounds in animals. The Greek hero Achilles is said to have taken it into battle to help heal the soldier’s wounds.
First Aid from the Garden
Astringent herbs help to stop minor bleeds, and dry weeping wounds or skin discharges (hot spots). Astringent herbs help create a dry, protective barrier covering the wound by coagulating serum proteins. The dry covering promotes wound healing by reducing infections, and prevents the wound from drying out. Create a tea from yarrow or carpet geranium leaves (2 teaspoons per cup of water) and use as a wash or spray. Sour fig juice can be used directly as it is. For mild diarrhoea, make a weak tea solution from sour fig, cinnamon, or carpet geranium.
Words of Wisdom
Tannin-containing astringent herbs should not be used internally for extended periods due to their potentially negative long-term effects on digestion, nutrient absorption, and liver function. Remember that diarrhoea can be Nature’s way of eliminating toxins and irritants and in many cases is self-limiting after a day or two. Because of the risks, animals with serious or on-going diarrhoea should be seen by a vet. Always consult your veterinarian if your animal is on medication, pregnant, lactating or undergoing surgery before using herbs.