The simple rule while travelling in Laos is not to drink river or tap water. Contaminated water is a major cause of sickness due to the presence of pathogenic organisms: bacteria, viruses and microscopic giardia cysts. These microorganisms cause diseases such as diarrhoea, gastroenteritis, typhoid, cholera, dysentery, polio, hepatitis A, giardia and bilharzia, and can be present even when water looks clean.
Safe bottled water is available almost anywhere, though when buying, check that the seal is unbroken as bottles are occasionally refilled from the tap. Water purifying tablets, carried with you from home, are an environmentally friendly alternative as they help to reduce the number of plastic bottles left behind after your travels.
Chinese tea made from boiled water is generally safe, but travellers should shun ice that doesn’t look factory-made. Some of the fanciest hotels have filtration systems that make tap water safe enough to clean your teeth with, but as a general rule, you’re best off using purified or bottled water.