The smell comes from IBA, if the gel is newly produced it has a strong smell. If the gel is old it doesn't have the smell which is also an indication that the hormone has somehow disintegrated. If IBA is exposed to light or warm temperatures it discomposes fast.
Be careful, it's not healthy and toxicity on humans is not well researched.
I have the 'secret' formula somewhere on a shelve, the carcinogenic substance is in a low dose like 0.03% and it's supposed to be safe if you don't eat it or touch the skin.