Anaphylactic reaction

There's a lot missing from your post. I assume there was a provider present who ordered the epi? What was the source of the anaphylactic reaction? Patient was allowed to leave because he "was in a hurry"?

Patient decided on his own to leave and signed a refusal of treatment form. I explained to the patient to patient that it would be in his best interest not to leave, another colleague also spoke to patient. It was the patients decision to leave

Protocol, first line of treatment for anaphylaxis is adrenaline

Do I understand that the patient noticed lip swelling at home, went to the pharmacy where he received Phenergan, and that after he took the medication, his lip swelling worsened? You then treated him for presumed anaphylaxis when he came to the clinic for routine lab work? The epi you gave him did not bring about improvement of his swollen lip?

He did not develop other signs or symptoms of respiratory distress such as tongue or facial swelling or difficulty breathing. You don't mention vital signs or other aspects of physical assessment. Did he c/o dizziness, weakness, have itching or a rash? Was he tachypneic, hypotensive?

Is it possible that his swollen lip may not have been caused by an allergic reaction?

My thoughts would be...what about adding a corticosteroid or at least an H2 blocker for this angioedema (no signs of anaphylaxis in your post) if no improvement after the Epi and there were concerns with giving another H1 blocker on top of the Phenergan ( I wouldn't expect cross-reactivity, but another H1 could lead to more EPS-like side effects)

Why were his lips only swollen on one side?