Pillows designed to alleviate ailments are aggravating neck-pain issues for some customers.
Sellers of bamboo pillows claim the products ease nerve pressure, support the neck and stop snoring.
But a health professional has said some people's conditions are worsening after using them.
New Zealand Chiropractors' Association vice-president Dr Hayden Thomas is aware of users of bamboo pillows who have experienced problems.
"What we've found with the bamboo pillows specifically is that some people find it sometimes forces their spine into a position they're not quite ready for, and that can aggravate symptoms with neck pain and stiffness and sometimes headaches."