Thiourea Test Paper.
Thiourea test paper by Precision Laboratories tests for the genetic capability to detect Thiourea. For other taste tests, see the PTC and Sodium Benzoate test paper.

Instructions:
Remove a Thiourea test paper from the vial.
Place the test strip on your tongue, and it will either taste bitter or it won’t taste like anything at all.
Note: The SDS for each taste test paper lists the ingredients. The concentration of ingredients is usually so small, it is less than what would be considered hazardous. Aside from these small quantities, the cellulose paper is the only other ingredient. In addition, the proper use of each taste test is to touch the strip to the tongue. These taste strips have been used safely in classrooms for decades.

The manufacturing facility where the PTC paper is produced (Cottonwood, AZ) is a typical manufacturing site. The side doesn’t manufacture nuts, gluten or other products usually associated with allergy concerns. Please note, however, that the facility is not certified or considered an allergy-friendly manufacturing facility. In addition, the raw materials used in producing the taste test papers are not procured in any special fashion. There is no assurance that they were produced in an allergy-free environment.

Despite the above information, if you have a concern about a possible allergic reaction, perhaps it would be best to abstain from the activity.

Documentation