I've been sneezing for 24 hours straight! Could allergies be the cause of this?

Sure. So could an irritant reaction to dust. Other symptoms of allergic rhinitis are nose, eye, and sometimes face and throat itching, nose stuffiness, runny nose, postnasal drip, and watery eyes. If an antihistamine - claritin, allegra, zyrtec, Benadryl (diphenhydramine) - stops the sneezing it's almost certain you have an allergy. Cherchez le chat and good luck.
May or may not be. Constant sneezing could be the result of a viral cold or from allergies. The crucial factor is itching. If it is accompanied by itching of nose, throat or eyes, it is allergic in nature. On the other hand if you have more of an achy feeling with burning in nose, sore throat, burning in eyes with or without fever it is probably a virus causing it.