|MadSci Network: Medicine|
Thank you for your question. Yes, adding methylene blue to food is dangerous. It is dangerous for two reasons.
The first reason is direct. Methylene blue is a biologically active substance. In medicine it is used to treat, among other things, methemoglobinemia. (More information on the causes of this disease including it's causes and treatments with methylene blue can be found on Heat hAnswers, an on-line magazine.) If methylene blue is administered inappropriately it can lead to a variety of health problems, principally among the very young. The following citations are links to abstracts of scientific papers detailing some of the possible complications of over-treatment with methylene blue:
J Pharmacol Exp Ther 1999 May;289(2):820-4 (Inhibition and stimulation of long-chain fatty acid oxidation by chloroacetaldehyde and methylene blue in rats)
Haemostasis 1998 Jan-Feb;28(1):17-24 (High doses of methylene blue/light treatment crosslink the A-alpha-subunit of fibrinogen: influence of this photooxidization on fibrinogen binding to platelets)
Pediatrics 1996 May;97(5):717-21 (Methylene blue-induced phototoxicity: an unrecognized complication)
Acta Anaesthesiol Scand 1996 Mar;40(3):382-4 (Pulmonary edema following intrauterine methylene blue injection)
Laryngol Rhinol Otol (Stuttg) 1986 Dec;65(12):699-701(Severe complications following the intrathecal administration of a methylene blue solution)
Far more serious is an indirect risk. Adding chemicals to food for pranks invites mistakes. Even when a chemical is known to be benign, there is a risk that it is kept in a solution that is toxic. A chemical and solution that is safe for most people may cause a severe reaction in a few people. It is because of these and other considerations that the Food and Drug Administration issues rules about what may and what may not be added to food. (If you have further questions about the appropriate uses of methylene blue in food, the FDA can be contacted through their web site.)
One final note: pranks and practical jokes tend to be played back and forth between people, with each new prank bigger (and more dangerous) than the last. Be very careful in initiating or continuing a trading of these.
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