I am working nights again after a year of day shift and finding it very hard to sleep during the day. safe sleep aids?

Sleep Hygiene First:: First, make sure you optimize your sleep environment! Black-out curtains, a comfortable sleep mask, & ear plugs are a great start. Consider white-noise & sleeping in a cooler setting. Avoid caffeine in the later half of your shift. Minimize natural light exposure on your way home (sunglasses!). Melatonin is a good place to start. Your medical history is important if considering other medication.

Better to go back...: to the day shift, as this the natural diurnal pattern we are genetically predisposed to live by. Working nights screws circadian rhythms up and leads to all kinds of physiological havoc. If you must, try Melatonin, Benadryl or even eat some turkey or take tryptophan (each separately--don't overlap). If exercise poops you out, try that just before sleep, or try sex--same idea.