Weiss addresses the question of carcinogenic compounds in the herb and the experiments done to establish their nature, but concludes ‘investigations of this kind may be of scientific interest but have no relevance whatsoever when it comes to practical therapy … all this has no bearing on the genuine value of the coltsfoot … The amount of the potentially carcinogenic pyrrolizidine alkaloids found in the dried plant drug was so small that it may be disregarded’. Weiss values the distinctive combination of mucilage and bitter, making coltsfoot a good tonic as well as a cough herb. He calls it the remedy of choice in chronic cases, especially for chronic emphysema and silicosis, diseases included in Priest & Priest’s specific indications. The leaves and flowers are used. He suggests a relief for the enduringly irritating morning cough for sufferers of these complaints by making a flask of coltsfoot tea, sweetened with honey, at night and keeping it by the bedside for use the following morning before rising, thus avoiding the unpleasant coughing spasms otherwise regularly appearing at the beginning of the day.
The British Herbal Pharmacopoeia notes the actions of coltsfoot as expectorant, antitussive, demulcent and anti-catarrhal; indicated for bronchitis, laryngitis, pertussis and asthma, with specific indications for chronic spasmodic bronchial cough, and may be combined with horehound Marrubium vulgare and mullein Verbascum thapsus in irritating cough. There is no recording of pyrrolizidine alkaloids here. Priest & Priest similarly carry no mention of the alkaloids and they designate it a diffusive expectorant, sedative and demulcent, with stimulant and relaxant auxiliary properties for debilitating and chronic conditions, especially with tubercular diathesis, specific for chronic emphysema and silicosis, pertussis and asthma. They recommend combining with elecampane or mullein for persistent cough. There are no references to smoking the herb, nor to external application of any kind, for skin inflammations nor for pectoral use.
Modern authors are more cautious about using coltsfoot, with reference to the pyrrolizidine alkaloids. Bartram rehearses its uses, yet adds a note that thyme and elecampane are preferable for internal use, nor should the herb be taken in pregnancy and lactation. There does, however, appear to be lingering appreciation of the herb. Williamson notes, as well as the list of pulmonary diseases addressed, how the polysaccharides are antiinflammatory and immunostimulant, as well as demulcent, and how the flavonoids have antiinflammatory and antispasmodic action, hence useful for coughs and colds. She argues the pyrrolizidine alkaloids have not caused problems in rats on low dose regimes and ‘appear not to cause damage to human chromosomes in vitro’. She suggests, however, that significant quantities should not be used. Chevallier argues the pyrrolizidine alkaloids are largely destroyed when the parts are boiled to make a decoction, but this is not supported by the evidence on safety (see below). He limits use though to the leaves, and for no more than 3-4 weeks at a time, and not in pregnancy and lactation, nor for children under 6 years old. Hoffman writes similarly though he cites Commission E’s more generous allowance of 4-6 weeks. Menzies-Trull records no caution among his comprehensive list of uses which reprise traditional applications including external use for chest and skin. He describes it as a favourite remedy in cough prescriptions. Wood suggests its use for liver and gallbladder, together with respiratory and other conditions. However, its main indication is as a lung herb and safety considerations preclude its use primarily for the liver.