First incident. In late 2005, I'm in Bangkok for business. On the 3rd or 4th night I ventured to an outdoor restaurant, and ate their "specialty" which was raw shrimp, garlic, and crushed chili. Yes, I was an idiot. On the walk back to the hotel I started to feel it. Broke out into a cold sweat, doubled over, and realized my meal was bad news. I managed to get back to the hotel and asked for help. I thought they would call an ambulance but instead they gave me some charcoal, which I had never even heard of before - but they convinced me to take it. I started to feel some relief after 30 minutes or so. I still felt terrible for a day or two, but I could tell it would have been far worse had I not taken it.
Second incident. In 2012 I'm in Madrid on Business, and a colleague and I met up at a somewhat empty restaurant. We split a paella, because we were foreigners and forgot we weren't in Barcelona. We went back to our separate hotels in different parts of town. I had some charcoal with me, and realized I needed to take some. I got back home fine, my colleague went back home and ended up in the emergency room - took her about 10 days to recover.
It's not something I take often (maybe once every two or three years). But I swear by it and always travel with it just in case an adventurous culinary experience ends poorly.