The whole plant is rich in a milky sap that flows freely from any wounds. This hardens and dries when in contact with the air[4]. The sap contains 'lactucarium', which is used in medicine for its anodyne, antispasmodic, digestive, diuretic, hypnotic, narcotic and sedative properties[9, 21, 46, 165, 192, 213, 238]. Lactucarium has the effects of a feeble opium, but without its tendency to cause digestive upsets[4], nor is it addictive[7]. It is taken internally in the treatment of insomnia, anxiety, neuroses, hyperactivity in children, dry coughs, whooping cough, rheumatic pain etc[238]. Concentrations of lactucarium are low in young plants and most concentrated when the plant comes into flower[238]. It is collected commercially by cutting the heads of the plants and scraping the juice into china vessels several times a day until the plant is exhausted[4]. This species is probably the richest supply of lactucarium[4]. The plant also contains 'hyoscyamine', a powerful depressant of the parasympathetic nervous system[213]. An infusion of the fresh or dried flowering plant can also be used[9]. The plant should be used with caution, and never without the supervision of a skilled practitioner. Even normal doses can cause drowsiness whilst excess causes restlessness[238] and overdoses can cause death through cardiac paralysis[7, 9]. Some physicians believe that any effects of this medicine are caused by the mind of the patient rather than by the medicine[213]. The sap has also been applied externally in the treatment of warts[222]. A homeopathic remedy is made from the plant[9]. It is used in the treatment of chronic catarrh, coughs, swollen liver, flatulence and ailments of the urinary tract[9].