Phrygian helmets were in vogue circa 1096 to 1170. so this would cover the 1st and 2nd Crusades, as the 3rd did not start until 1188. but no doubt they were probably worn during the 3rd and maybe the 4th as well.
Conditions were very unsanitary... so much that when the soldiers were sailing into the Crusades for battle, about 1/4 of the men died from disease itself.