Similar thing happened to me last year; I've never been able to tan evenly and had experienced a bad sunburn at least once every single year that I could remember. Tried it out and combined it with the tanning booths for 5 mins at a time twice a week. Started to get darker gradually until one day I woke up in the morning and when I was brushing my teeth I looked in the mirror and freaked out on how dark I was overnight (from the building, cumulative effect).
The wife won't let me use it anymore