Is it dangerous to use expired cake mixes?

Dangerous? What an odd choice of words.

No, it's not 'dangerous' to consume or use food products after the sell-by/use-by dates.

It's all about common sense. Cake mixes don't go bad.

Best-before doesn't necessarily mean poisonous after.

craftermom, your screen name indicates more of a casual rather than a business relationship with caking but i don't know for sure -- but if you were a business the quality of the cake would probably be lower than a fresh cake mix and you might want to punch up the leavening and add a shot of vanilla -- you could do the same for home use of course -- but for a business i would not use any out of date ingredients so that i could give the best report in the event it was ever requested --

best to you

I don't think it would hurt you to eat an expired mix, but I would be concerned the leavening is dead and you'd end up with sweet hockey puck 

Thank you for your replies - I did some research and discovered that it would be unsafe to eat if it had been opened and mold had occurred and if someone with mold allergies had eaten it.  That was not the case here so I baked it and it came out great. I always use the extender recipe and I got 1 - 8" round, 1 - 6" round and 12 cupcakes. And they all raised wonderfully!  And I even ate a cupcake with no ill effects.

What is the extender recipe?  

To all of my cake mixes, I add the required ingredients plus I always add 1 cup sour cream, 1 cup flour, 1 cup sugar, 1 extra egg, 1 teaspoon vanilla and 1 t. Almond flavoring.  

In most cases, unless something actually molds, foods just gradually lose quality over time.  So if something has a 6 month outdate, it's likely to still be fine after 7 or 8 months, but after a year or longer it may not work as well.

As mentioned, things don't suddenly become unsafe as soon as they expire, that's just the limit of how long the manufacturer will guarantee that's it's going to be at top quality.  Many foods (and drugs and other things) are perfectly fine for quite a long time after they expire.   They may not be quite as perfect, but anything truly dangerous can usually be detected just by looking at and smelling it, and using common sense.