What age can a child start sleeping with a pillow? What type of pillows are the safest?

Hello and thank you for your question!
Red Nose does not recommend pillow use for infants and young children. They are an unnecessary addition to a baby’s sleep space and increase baby’s risk of sudden unexpected death in infancy including SIDS and fatal sleep accidents
Red Nose recommends delaying offering a pillow until baby is over two years of age and is no longer sleeping in a cot or portable cot
As such, Red Nose does not recommend a specific brand of pillow for purchase.
Thanks again! 

Pillows are not necessary for baby and increase baby’s risk of sudden unexpected death in infancy including SIDS and fatal sleep accidents
Red Nose recommends delaying offering a pillow until baby is over two years of age and is no longer sleeping in a cot or portable cot
https://rednose.org.au/article/pillow-use