Borax is a miracle sustance, it is also the most effective roach poison I know. I would be very careful about doing any such thing.
Do a google search...here is just one of the many things you will find...
The Borax Conspiracy - How the Arthritis Cure has been Stopped – by Walter Last
http://www.health-science-spirit.com/borax.htm
And btw, diatomaceous earth kill insects. Food grade DE is safe and effective for live stock, pets and humans. Among other things, it kills intestinal parasites, something we all have if we don’t deal with them.
The point of the comment about DE is that many things kill insects, but are safe for humans. Table salt, is poisonous, if you consume enough. Sodium tetraborate decahydrate is safer than table salt, sodium chloride.
Breathing pure oxygen can be deadly...we need some carbon dioxide to trigger the breathing reflex. Water can be deadly...even drinking too much.
And while we are on the subject of ‘deadly’, many, many pharmaceutical drugs are deadly, even at prescribed doses...and these have FDA approval. Think about it...I would be very careful about taking ANY prescription medicine.
Boric acid has many uses too, including being used as an eye wash. For internal use, Borax has a much lower toxicity than Boric Acid.