How would you go about removing allergens from a couch?

I brought home a couch that I purchased for a symbolic amount and I don’t know what has happened to this couch in the past.

I have had an allergic reaction worthy of a visit to the hospital last week. I wonder if it’s related. I’ve been sitting on this couch for about two months with no issues though.

In any case, would you know of a way to kill allergens on a couch? What do you recommend?

Thanks!