Many recipes for medicines included herbs, minerals, and pieces of animals (meats, fats, skins) that were ingested, made into paste for external use, or used as aromatherapy. Some of these are similar to natural remedies used today, including catnip, chamomile, fennel, mint, garlic, and witch hazel. Many other ingredients used in the past such as urine, fecal matter, earwax, human fat, and saliva, are no longer used and are generally considered ineffective or unsanitary. Trial and error were the main source for finding successful remedies, as little was known about the chemistry of why certain treatments worked. For instance, it was known that drinking coffee could help cure headaches, but the existence and properties of caffeine itself was still a mystery.