We say "have nausea", not "have a nausea". The noun "nausea", being uncountable, doesn't take the indefinite article "a".
We say "have nausea", not "have a nausea".
My child has nausea and vomiting.
My child has a nausea and vomiting.
The noun "nausea", being uncountable, doesn't take the indefinite article "a".
Some people have nausea after surgery.
Having nausea and fatigue can be quite common in summer.
Follow the same convention with the expressions "cause nausea", "experience nausea", "relieve nausea", "prevent nausea", etc.
Pregnant women may experience nausea and vomiting.
You can relieve and prevent nausea by drinking ginger tea.
Be aware, however, that we frequently use a possessive pronoun before the name of this symptom.
When your nausea subsides, you can eat larger meals.
A partial list of other symptom names that do not take a/an:
