After about a month into our relationship and sharing a bed together, we discovered we had Scabies (caught from a friend who stayed over and
used our towels, bedding etc). My partner had a VERY bad reaction to it, and it was much more visible and clearly more irritating to him than me. We used at LEAST 10-15 applications of Permethrin 5% cream, all over, left for 12hrs at a time over a good few months... The Scabies took a LONG time to get rid of.
Now, thankfully the Scabies has gone.