Final answer:
The client should not wash his hair before an EEG as it can interfere with the electrodes' ability to detect electrical signals from the brain. Additionally, the gel or paste used during the test may be removed if the hair is washed.
Step-by-step explanation:
The client should not wash his hair before an EEG. The reason for this is that the electrodes used to measure brain activity during an EEG need to make direct contact with the scalp. If the hair is washed, it can interfere with the electrodes' ability to detect electrical signals from the brain.
Additionally, some EEG tests may involve the use of a gel or paste that helps improve the conductivity between the electrodes and the scalp. Washing the hair before the test may remove this gel or paste, making it difficult to get accurate readings during the EEG.