What is the mechanism of itching?

A 37yo female working as a healthcare assistant in a nursing home comes to the ED with
complaints of severe itching all over her body. On asking she replies that she had applied cream
on the body of a resident in the nursing home who had similar itches. What is the mechanism of

a. Allergic reaction
b. Inflammation of keratinocytes c. Allergic reaction developed due to use of topical steroid creams
d. Subcutaneous bleeding
e. None

Ans. The key is A. allergic reaction