memai ga suru toki wa, muri ni gaishutsushinai hou ga ii desu.

topic particle

Breakdown of memai ga suru toki wa, muri ni gaishutsushinai hou ga ii desu.

• です: to be
• が: subject particle
• いい: good

Questions & Answers about memai ga suru toki wa, muri ni gaishutsushinai hou ga ii desu.

Why is it めまいがする and not めまいをする?

Because めまいがする is the standard Japanese expression for to feel dizzy / to have dizziness.

• めまい = dizziness, vertigo
• する = to do, but in many expressions it works more like to occur / to be felt

With physical sensations and symptoms, Japanese often uses noun + がする:

• 音がする = to hear a sound
• においがする = to smell something
• 咳がする = to have a cough
• めまいがする = to feel dizzy

So here, が marks the symptom being experienced.

What does ときは mean here?

とき means when or at the time when.

In this sentence:

• めまいがするとき = when you feel dizzy
• ときは adds は, which marks that time/situation as the topic

So めまいがするときは means something like:

• As for when you feel dizzy, ...
• When you feel dizzy, ...

The は gives it a general advice / topic-setting feeling.

Why is there a は after とき?