Never use shampoo straight from the bottle. Take a bigger, translucent, container, pour the shampoo into it, and dilute it with water. You may go for a 50% shampoo-50% water solution, or a 30% shampoo-70% water solution. Shake well. This makes your shampoo milder and prevents your scalp from developing itches and pustules.

After shampooing your hair, rinse off immediately, and rinse off well. Do NOT keep the shampoo on while soaping and scrubbing the rest of your body. While it makes a pretty picture, it is not good for your scalp.

Using the same brand of shampoo is like smoking the same brand of cigarettes for too long--you develop smoker's cough and must temporarily switch to another brand.

In the end, of course, you can live without smoking,

In fact you can also live without shampoo.