Dairy products must originate from pasteurized milk and be well refrigerated or else should not be ingested. Waterborne disease is due to fecal contamination of the water used to drink or to brush teeth. Risk of diarrhea may be reduced by careful attention to the quality of water ingested. Commercially bottled water is a good source. Commercially carbonated beverages are generally safe, being slightly acidic.
Beer is free of enteric pathogens.
Rain water, properly collected and stored, may be considered fit to drink. Water may be treated by heat, filtration, or with chemicals. Tea and coffee prepared from boiling water and served hot are safe drinks. Filters that work according to particle size are effective against bacteria and parasites but not against viruses. Chlorine, available in commercial household bleach, is effective against most pathogens, but relatively ineffective against Giardia lamblia cysts.