"Even if the walnuts are crushed down to powder form, they can damage and cause micro-tears in the skin.
The skin specialist went on to explain that not only will the product damage the skin, it could also cause visible signs of premature ageing - due to increased exposure to daily aggressors.
Kylie Jenner's press team were contacted by Metro.co.uk but are yet to respond.
The 21-year-old announced her new line on Instagram last week.
Fresh-faced and dressed in a pink dressing gown, the reality TV star says: "Let's talk about walnut scrub.
"So my walnut face scrub is really gentle, it's gentle enough to use it every day. I recommend two or three times a week, that's how much I use it. Some walnut face scrubs are kind of harsh on the skin, this isn't too abrasive.
"It really leaves my face feeling super baby soft, makes me look glowy, takes away dead skin cells. My walnut face scrub is my secret to a fresh face."
One Twitter user posted an image of Samantha Jones from Sex and The City after the character had a bad reaction from a chemical peel, with the caption: "Kylie Jenner's walnut face scrub does wonders".