Question: what can cause unexplained nausea?
Answer: Motion sickness or seasickness.
Early stages of pregnancy (nausea occurs in approximately 50%-90% of all pregnancies; vomiting in 25%-55%)
Medication-induced vomiting.
Intense pain.
Emotional stress (such as fear)
Gallbladder disease.
Food poisoning.
Infections (such as the "stomach flu")