When using essential oil mixed with shampoo on your baby's scalp, first confirm if this is suitable for baby's skin by doing a patch test. If the patch test succeeds, you can move forward and apply the mixture to their scalp. Don't leave it on for too long and gently massage the shampoo for a minute, then rinse thoroughly. Their scalp is still sensitive, so it doesn't require thorough cleaning. Don't use tea tree oil on babies below age 3 months.