This is a 40 y.o. female who presents with abrupt onset of nausea vomiting, diarrhea, myalgias, headache about 2 hours after receiving her 1st Moderna COVID-19 vaccine at 1300 hrs..  She describes myalgias extending from the area of her left deltoid injection site over her shoulders and over her entire upper body.  No neck or back pain.  She describes diffuse throbbing headache with no positional component.  She has had relentless nausea vomiting and retching.  She has been up vomiting stomach contents to bile multiple times.  She has had loose watery brown diarrhea multiple times.  She describes diffuse abdominal crampy pain with increased tearing retching and vomiting.  She denies any shortness of breath cough or wheezing.  Voice is normal.  No swallowing dysfunction or pain.  No intraoral or facial swelling.  She denies rash or pruritus.  No arthralgias.   Patient reports prior anaphylaxis with shortness of breath and tight airways, difficulty speaking and swallowing, and relationship to coconut ingestion few years prior.  No other known food/nut reactions.   Patient is a CNA for care at home.  Last Covid test was 2 weeks ago which was negative.  She reports she has been tested every 2 weeks routinely.    Review of Systems   Cardiovascular: Negative for chest pain and palpitations.  Gastrointestinal: Positive for abdominal pain, diarrhea and nausea. Negative for vomiting.  Musculoskeletal: Positive for myalgias. Negative for arthralgias, back pain and neck pain.  Neurological: Positive for headaches. Negative for dizziness, weakness and numbness.   Physical Exam BP 126/73  | Pulse 120  | Temp 37.1 °C (98.8 °F)  | Resp 18  | Ht 1.575 m (5' 2")  | Wt 68 kg (150 lb)  | SpO2 100%  | BMI 27.44 kg/m²    ED Course as of Dec 30 2340 Wed Dec 30, 2020 2128 Reevaluation: Nausea improved.  Abdominal cramping resolved.  No further diarrhea or vomiting.  Still complains of headache and muscle cramping through her upper shoulders and arm.  Will remedicate with steroid and acetaminophen  2258 Reevaluation: Patient improved.  Pain/myalgias improved.  Headache now mild and dull.  Continues with no further.nausea vomiting or diarrhea.  She would like to try fluids at this time.  Assuming toleration we will plan on discharge home.  2326 Reevaluation: Patient feels improved.  Headache essentially gone.  Taking p.o. fluids well.  Discharge instructions discussed.  She is very familiar with an EpiPen because of her daughter's prior use.  Discharge instructions discussed.    ASSESSMENT and PLAN   This is a 40 y.o. female who presents with nausea vomiting diarrhea, myalgias, diffuse abdominal cramping, severe global headache, onset about 2 hours after first dose Moderna COVID-19 vaccine.  Exam with intact mental status, neurologic system.  Abdomen with some diffuse tenderness but no evidence of peritoneal sign.  She had diffuse palpable soft tissue muscular type tenderness through her upper extremity shoulder and bilateral paraspinal back.  She had no meningeal signs.  She had no cardiorespiratory signs or symptoms.  Her chest was clear.  Voice normal.  Swallowing normal.  Oropharyngeal region normal.   Initial ED ED management focused on rehydration, antiemetics and subsequent treatment for presumptive anaphylaxis with likely system involvement gastrointestinal and neurologic.  She was treated with Solu-Medrol, famotidine and acetaminophen.  She improved during ED course and did not require epinephrine.  Symptoms at ED reevaluation/discharge were resolved.   Clinical impression favors anaphylaxis over medication side effect given time course and abrupt onset of symptomatology and signs.  She has a distant history of anaphylaxis to coconut-based product in her past.  She has no history of ongoing allergic chronic history otherwise.  Other organ systems appeared stable at onset and through ED course including cardiovascular and pulmonary.   Plan is for discharge home with rest fluids.  She will have a course of steroids/prednisone and famotidine.  She was sent home with an EpiPen and understands use and precautions.     Discussed ED "return immediately if" parameters with patient. Ongoing FOLLOW UP evaluation/care coordination via PCP recommended. Patient voices good understanding of current evaluation, follow-up & return recommendations and discharge instructions.   Encounter Diagnosis Anaphylaxis due to vaccination, initial encounter   Plan: -d/c home.  No work next 2 days.  Off work note provided -COVID-19 testing pending -rest with activity as tolerated -diet as tolerated & increased fluids as discussed -acetaminophen PRN -Prednisone 40 mg daily to finish 4 more days -Famotidine 40 mg daily to finish 4 more days -Zofran as needed (patient has at home) -Loratadine 10 mg OTC as needed -PCP f/u -ED return for interval worsening -instructions discussed & as documented