Taming Poison Ivy's Itch.

It is no secret that direct contact with poison ivy causes an uncomfortable agonizing itch. How this happens is still not clearly defined. As reported in ACS News online, Sven-Eric Jordt of Duke university pinpointed a molecular pathway that helps transmit an itch signal through nerve cells by exposing mice to poison ivy’s oily allergen urushiol. Two commonly prescribed drugs to fight the poison ivy itch are antihistamines and corticosteroids. Unfortunately antihistamines seem to not work and although corticosteroids fight inflammation they are ineffective against itch.  Jordt looked for genes that were transcribed at higher levels in mice whose skin was brushed with urushiol compounds compared to non-exposed mice. 

As expected several genes associated with inflammation were up regulated in the infected mice, but Jordt focused on one particular gene that codes for the protein interleukin-33, associated with itchy skin. When the exposed mice were given antibodies against IL-33, the mice slowed their scratching significantly. When exposed mice were given antibodies against IL-33’s receptor, ST2, which is located on sensory neurons that connect to the animals’ skin, also significantly reduced itching.  Researchers suspected a link such as this one but did not know the specifics. Even though a molecular pathway for itch is complicated, these systems will share features important for future drug design. Jordt’s team hopes to work with clinicians to see if they can detect IL-33 in humans with poison ivy.