posted 6 years ago
The method (I know) is an old folk one, and can take days, if you're very careful. It begins with touching the part in question to a sensitive spot in your skin - like the inside of your wrist, then your lip, then the tip of your tongue, then, in your mouth, then actually swallowing a tiny amount. Between each testing, you wait at least a few hours & up to a day, to see if you have any reaction to it, like tingling, burning, rash, nausea, swelling, etc.
But, if you can find out from someone with experience, or a solid resource, that's better, imho - and likely a LOT faster!