Laxatives are medicines used to relieve constipation by making stools softer or easier to pass. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says a health care professional may recommend one for a short time when changes to diet, fluids and activity are not enough.
The main over-the-counter types are fiber supplements (such as psyllium or methylcellulose), osmotic agents (such as milk of magnesia or polyethylene glycol), stool softeners (docusate), lubricants (mineral oil) and stimulants (such as bisacodyl). NIDDK advises using stimulant laxatives only for severe constipation or when other treatments have not worked, and talking with a doctor if you cannot have a bowel movement without them.
Source: Treatment for Constipation, NIDDK (National Institutes of Health)
Image: Psyllium seed husks by Bastique (Cary Bass), CC BY-SA 3.0, via Wikimedia Commons.