If using Olive Oil for newborn baby's hair does that mean?

If I am using Olive Oil for a newborn baby's hair as I read that it is better to use natural oils such as: Almond, Walnut, Coconut, etc. (but babies could be allergic to these so I am going with Olive oil) should I buy the Olive oil like cooking olive oil from down the grocery store oil aisle or from where? The problem with Olive oil in hair stores as I have being doing my research they have ingredients in them that are very harmful not only to babies but adults. My hairdresser is all about using natural products so she was telling me think about what your doing to your brain when you apply all those harmful ingredients and she advise me to not use baby oil as the ingredients are somewhat harmful as well. Anyways so yes where do I buy the Olive Oil for straight natural Olive Oil and not ones with other ingredients (that are not natural in them)??? Thanks in advance