How a poison (Toluene) may be encased in an sulfa allergen base (sulfonamide)  for a terrible reaction.

eg ... Ethyltoluene Sulfonamide used in dental sealants, root canal liners etc...

Toluene Info Below.

http://www.emedicine.com/emerg/topic594.htm

Sulfonamide  info below.

http://en.wikipedia.org/wiki/Sulfonamide_(medicine)

Sulfonamides have the potential to cause a variety of untoward reactions, including urinary tract disorders, haemopoietic disorders, porphyria and hypersensitivity reactions. When used in large dose, it may develop a strong allergic reaction. One of the most serious is Stevens Johnson syndrome (or toxic epidermal necrolysis).

Researched after seeing the following information.

http://www.icnr.com/dentalsealants/DentalSealantToxicity.pdf

Toluene is a known potent nerve toxin associated with the neurological symptoms of NCS. The sulfonamide component of this compound brings about a sensitivity allergic toxic reaction ultimately manifesting as vascular mucoid sores characteristic of the NCS, especially in sulfa sensitive patients.