What causes the scent that I smell after tanning?

In a word, “melanin” is the cause. Ultraviolet light in the UVA range causes melanin to enlarge and turn brown. During the process, dermatologists say a chemical reaction takes place. A natural side effect of the reaction is the aroma. This occurrence is normal whether you've been tanning inside or outside. Some tanning lotions have been designed to minimize or prevent the odor from occurring, but ultimately a shower will remove the odor.