Differential Diagnoses for Young Female with Smell Sensitivity and Vomiting

Immediate Priority: Pregnancy Testing

Pregnancy must be excluded first in any woman of childbearing age presenting with nausea, vomiting, and smell sensitivity, as it is the most common endocrinologic cause of these symptoms, according to the American Gastroenterological Association 1
Nausea and vomiting of pregnancy typically begins at 4-6 weeks gestation, peaks at 8-12 weeks, and is commonly associated with heightened smell sensitivity due to elevated human chorionic gonadotropin and estrogen levels, as recommended by the American College of Obstetricians and Gynecologists 1
The combination of smell sensitivity and vomiting lasting 2 weeks in a young female strongly suggests early pregnancy, with a high level of evidence from the American Gastroenterological Association 1

Diagnose as nausea and vomiting of pregnancy (NVP) and assess severity using the Motherisk Pregnancy-Unique Quantification of Emesis (PUQE) score to determine if this has progressed to hyperemesis gravidarum, as recommended by the American College of Obstetricians and Gynecologists 1
Early treatment is critical to prevent progression to hyperemesis gravidarum, with a moderate level of evidence from the American Gastroenterological Association 1
Initial management includes vitamin B6 (pyridoxine 10-25 mg every 8 hours) combined with doxylamine, which is FDA-approved for this indication, with a high level of evidence from the American College of Obstetricians and Gynecologists 1

The second most likely diagnosis is post-viral olfactory dysfunction with associated nausea, particularly COVID-19 or other viral upper respiratory infections, as reported by the American Rhinologic Society 2, 3, 4
Anosmia (complete smell loss) or altered smell perception (parosmia) occurs in 59-86% of COVID-19 patients and can present as the initial or isolated symptom, with a high level of evidence from the American Rhinologic Society 2, 3, 5
Post-viral smell dysfunction typically develops 1-4 days after infection onset, with 73% of patients experiencing recovery within 7-14 days, though 20% have symptoms persisting beyond 14 days, as reported by the American Rhinologic Society 3, 4

Viral gastroenteritis: Usually self-limited with sudden onset, mild fever, and diarrhea, but 2-week duration makes this less likely, as reported by the American College of Radiology 6
Food intolerance or formula intolerance: Can cause persistent vomiting but less likely to cause smell sensitivity, with a low level of evidence from the American College of Radiology 6

Increased intracranial pressure: From tumor, trauma, or other causes, though this would typically present with headache, neurologic signs, or altered mental status, as reported by the American College of Radiology 6

Metabolic disorders: Including diabetic ketoacidosis, thyroid disorders, or adrenal insufficiency, though these would typically have additional systemic symptoms, with a low level of evidence from the American College of Radiology 6

Step 1: Obtain urine pregnancy test immediately, as recommended by the American College of Obstetricians and Gynecologists 1
Step 2: Detailed history focusing on temporal relationship to any viral illness, character of smell sensitivity, presence of nasal congestion or rhinorrhea, and medication history, as reported by the American Rhinologic Society 2, 3, 4
Step 4: Initial laboratory testing if indicated, including COVID-19 testing if post-viral etiology suspected, as recommended by the American Rhinologic Society 2, 3

Failing to test for pregnancy first in any woman of childbearing age with nausea and vomiting, as recommended by the American College of Obstetricians and Gynecologists 1
Dismissing smell sensitivity as unimportant: This symptom strongly suggests either pregnancy or post-viral olfactory dysfunction and should guide the differential, with a high level of evidence from the American Gastroenterological Association and the American Rhinologic Society 1, 2
Not recognizing that COVID-19 can present with isolated olfactory symptoms: Anosmia can be the only presenting symptom without typical respiratory manifestations, as reported by the American Rhinologic Society 2, 5