I thought charcoal was a carcinogen but you can buy charcoal biscuits for humans in pet shops and for cats and dogs and other animals in pet shops. Why would you want to eat something dangerous?

Charcoal when burnt for cooking meat, which contains fat, MAY contain potentially carcinogenic substances (but that is not proven). In complete contrast easting pure charcoal (humans or pets) is NOT carcinogenic.

David,

As to why you (or any other creature) might eat charcoal is, presumably, due to the chemical properties contained within (predominatly carbon), which can aid digestion, much as a calcium carbonate tablets (like Rennies ) do?

I've heard of charcoal being used to reduce poisoning but I have no idea if that is substantiated...

Following on from Dave, charcoal is very absorptive for a number of substances e.g., steroids, so I guess a low concentrations it might be used to prevent certain substances from leaving the stomach. I wouldn't be surprised if a chef like Hestor Blumenthal had incorporated it into a porridge or desert though!!

It is a much more mundane reason I am afraid - the charcoal is said to absorb and neutralise excess gas so reduces burping and bad breath (in humans and pets). That said the amount of hard data to support those ideas is lamentably lacking (which of course does not stop health food and pet stores selling them for that purpose)!

Dave is however correct - medically we use it in casualty/ER to reduce absorption of many tablets when people have taken overdoses. See
http://www.emedicinehealth.com/activate … cle_em.htm

Charcoal is also used to filter drinking water because it absorbs organic impurities, some of which could be carcinogenic.

In the UK all drinking water is rigorously tested for impurities (carcinogenic or otherwise). Thus filtering UK tap water through charcoal will make it taste nicer but I wouldn't want anyone to misinterpret your post Brent and think our potable water is or could be carcinogenic!