Are there limits on how much you can reduce your alar base?

The limiting factor for narrowing the base of the nose for most patients is the size of their nostrils. It is important to get air through the nose. Several techniques can be used to narrow the nose. Sometimes increasing the support to the tip can help to narrow the nose. The skin of the side of the nostril can be excised( weir or alar base resection ).

There is a limit due to deformity of the alar margin the more you tighten.  A combination of excision of the alar base skin and a cinch procedure is your best bet.  However, if excising too much, the shape of the ala can be adversely affected including asymmetries that may pop up.  It is best to be conservative when approaching the alar base.  Once cm is excessive.  Best wishes, Dr. T. 

The ultimate limit will be the point at which alar base reduction starts to close your nostrils down so much that it affects your breathing

There definitely are limits as to by how much the alar base can be reduced. 1 cm total (5 mm on each side) seems like a lot. Please note that alar base reductions are not the only means to narrow nostrils and/or alar bases. Furthermore, there are many different types of alar base reductions. Changing the nasal tip position itself can change the alar base width as well. I recommend you see an experienced rhinoplasty expert for a consultation for a detailed and comprehensive analysis that is not limited to your alar bases only. Best wishes!

There are limits to what can be done with rhinoplasty. One centimeter would be a lot to reduce from your alar base, and I personally have never removed that much tissue. All of that said, if your anatomy included an excessively wide alar base, then a 1 cm removal could be appropriate.  I would recommend consulting with a board certified facial plastic surgeon who regularly perform rhinoplasty to explore your options. Especially if considering maneuvers that extreme, you would want a surgeon extremely proficient in nasal surgery.