Azulenes are hydrocarbons in the distillation process of compounds in the essential oil. They are found in the essential oil of yarrow, wormwood, chamomile and Roman chamomile. They are anti-inflammatory and anti-allergic. Most is used externally, except guaiazulene, which is administered orally as a drug for treatment of bronchial asthma and allergic conditions. Urine takes the green colour, although azulenes, as free compounds, have also blue and violet colour.