New Flannel Sheets Smell Like Gasoline After Washing

I recently purchased new flannel sheets for my children's beds. My son has been sleeping (I washed it first) on it for the past two weeks and his asthma has been terrible. I was thinking it was from the outside air. However, I took their sheets off this morning and washed them again. When I took them out of the washer I noticed a very strong chemical smell, almost like gasoline. Is this possible? Would I be better off purchasing old second hand cotton sheets for my children to sleep on?