Client reported feeling itchiness on the back of the head and both arms as well as aching in bones to, RN at 11:22 after receiving the 2nd dose COVID vaccine (Pfizer, Lot #FD0809) in the L arm on 09/07/2021. RN took client vitals, transferred client to zero gravity chair, and provided client a water bottle. Client vitals at 11:23 were BP 130/80 in the R arm sitting upright, HR 70, and RR 15. Lead RN assessed client who presented A&O x4 and denied SOB, chest pain, tingling, numbness, dizziness, and trouble swallowing. No redness or swelling observed. Client stated she did not have an adverse reaction to the 1st dose COVID vaccine and has NKDA. At 11:26 client reported itchiness was was now located at her legs, arms, and back of head. RN offered client IM Benadryl to relieve itchiness and client provided verbal consent.  RN drew up 50mg IM Benadryl and RN administered 50mg IM Benadryl in the R arm at 11:26am. Client reported she is not currently taking medication and has no chronic conditions or significant health history. Client took sips of water. At 11:31 RN took client vitals with BP of 135/90 in the R arm sitting upright, HR 135/90, HR 74, and RR 16. At 11:32 client stated the itching was decreasing on her legs and arms but continued on the back of head. Client denied numbness, tingling, swelling, SOB, and trouble swallowing. Client reported body aches were improving but still present in lower legs. Vitals were taken by RN at 11:38 with BP 112/80, HR 72, and RR 16. At 11:40 client reported feeling mild dizziness. Lead RN provided client with juice box, nutrigrain bar, and water bottle. Client took sips of juice and water, and ate the nutrigrain bar. RN educated on side effects of Benadryl, advised client to remain in observation for another 30 minutes, and advised client to call a friend or family member to pick her up from the vaccine site. RN took vitals at 11:43 with BP 128/82, HR 64, and RR 16. Client reported that itchiness and aching was gone in her arms and legs but was still experiencing mild itchiness on the back of her head and neck. At 11:48 client vitals taken by RN were 130/80, HR 68, and RR 14. At 11:55 client denied dizziness while sitting down. Lead advised client to stand up with assistance to assess for dizziness. At 11:58 client stood up and reported mild dizziness. RN advised client to remain in zero gravity chair and provided juice box and chips. Client finished both juice and chips. At 12:08 RN took orthostatic BP: 124/82 sitting down and 130/80 standing up. At 12:11 client reported her itching and dizziness had completely subsided. Client reported she had only had coffee in the morning before receiving the vaccine and stated the "juice and snacks helped a lot". At 12:20 client reported she was unable to find someone to drive her home. Lead RN advised client to contact ride share or taxi services but client declined. At 12:25 client presented A&O x4 and denied dizziness, changes in vision, tingling, numbness, trouble breathing, and chest pain. At 12:28 RN assisted patient with standing up and assessed for dizziness, client denied dizziness when standing, no imbalance or distress while standing was observed. RN observed client walking around the room with a steady, balanced, and symmetrical gait. Client denied dizziness when walking. Lead RN reviewed ER precautions, when to f/u with PCP, and health authority information. At 12:35 client left the vaccine site.