Are you sure that hey are not either ofthe following:
small blisters or heat rash? (I had this once and yes they itch)
-the blisters were so tiny that I could hardly even tell thatt hey were blisters, my doctor had to actually point it out, that they were blisters and not just "bumps".
an allergic reaction to your tanning lotion?
-sometimes when you continually use the same lotion your body begins to "reject it" same reason why woman who start wearing make up very early tend to NOT be able to wear it later in life, because they become llergic to it.
have you changed your tannign lotion recently?
-also could be an allergic reaction... or sometimes the "hot action" lotions can cause red bumps and a tingly/itchy sesnation for up to 6 hours after you tan, or until you shower to remove it.
Try covering just your tummy with a towel while you tan, and don't apply any tanning lotion or accelorator to the area, for a couple times and see what happens... *i know that you don't want a tan line* but the stomach is usually the first area to tan, gets the darkest and also absorbs the most heat in the bed. If it still happens, it could have something to do with the heat and NOT the bed or the lotion itself.
you could also see if an aloe based "after tanning lotion" helps.
If NONE of this works, I would recommend stopping tanning, and seeing your doctor about it before starting again.
**my aunt and uncle owned a tanning salon for 5 years, I both worked and tanned there for a long time, so I've seen alot of crazy stff... probably more than I wanted to... lol**
we also own a tanning bed and have for a REALLY Long time... I've been tanning since I was in about 8th - 9th grade.
BTW to keep from getting wrinkles from tanning... exfoliate, exfoliate, exfoliate... lol cause unfortunately it IS true... you do get wrinkles from tanning... =)