PT14.S4.Q21 — What is the definition of "solely?"

Hey all,

I'm having trouble translating the conclusion of the argument into logical form, perhaps because of the word "solely." The conclusion states that "it is solely due to ... peppers that he became ill."

I interpreted solely as only (and therefore required), so my diagram was like this:

~ peppers --> ~ sick

sick --> peppers

This is contrary to the explanation here: https://classic.7sage.com/lsat_explanations/lsat-14-section-4-question-21/

Can someone explain how I should interpret solely?

Thanks!