College of Massage Therapists of British Columbia (CMTBC) Practice Exam

Which of the following has a chemical effect on the skin?

1. Paraffin wax

2. Mustard plaster

3. Heat application

4. Cold compress

The correct answer is: Mustard plaster

The choice of mustard plaster as having a chemical effect on the skin is based on its active ingredients, which typically include mustard powder. When applied to the skin, mustard plaster generates heat through a chemical reaction, leading to increased circulation and the release of irritants that cause a warming sensation. The mustard oil, when absorbed, can lead to localized skin effects, including increased blood flow and sometimes a reddening of the skin due to its irritating properties. This aligns with the definition of a chemical effect, as it involves a reaction that alters the skin's condition. In contrast, paraffin wax primarily provides a thermal effect by retaining heat and helping with the treatment of certain conditions through its warming properties without a significant chemical interaction with the skin. Heat application and cold compresses also act mainly by altering temperature and blood flow but do not have a chemical effect in the same way that mustard plaster does.