My Son Just Had A Anaphylatic Reaction To Walnuts We

my son just had a anaphylatic reaction to walnuts we have known since he was 2 years about his peanut allergy , he is now 24 years.He was admitted to the local ER . He was given epi and steriods . He rebounded back well but he is still very tired from the event .Is this normal to be very tired for 2 days after and is there any residual from the meds that he would have?