If allergies are causing you nasal congestion, you may end up breathing through your mouth when you sleep, and doing so will likely cause snoring. You can also end up with a poor night’s sleep and a headache the next day.
Allergies generally come from the environment, so the place to start eradicating their source is your bedroom. If you sleep with your pets, there’s a good chance they’re bringing little buggies with them, and these buggies can definitely affect your sinus passages. Best: remove the pets to the floor or another room. Good: clean your bedding continually (what a pain, huh?) and spray the mattress with an anti-bedbug spray.
The latter, in fact, is a good idea even if you don’t have pet, as bugs (mites and the like) can make it to your mattress very well on their own. So spraying the mattresses and cleaning the bedding frequently is always a good idea. You may also wish to buy a sterile mattress cover to keep those little devils away.
You should also regularly clean your heating/air-conditioning filters, along with regularly vacuuming the carpets and cleaning all the places where bugs can accumulate.
Now if your allergies are borne of outside particles from trees or bushes, you’re probably going to have to do more than take preventative steps. You’ll also need to treat the symptoms of the allergy, which generally include a blocked nose.
A variety of nasal decongestant sprays and pills are available, some more effective than others. A nasal saline flush can also provide relief, though it’s usually just temporary. Antihistamines can definitely resolve the symptoms but may yield a “sleep hangover”; they should not be taken long-term, however. Nasal decongestant pills or liquids can provide long-term relief, but they may also disrupt sleep, especially if they contain pseudoephedrine or phenylephrine.
The main point is to recognize that allergies can definitely cause sleep problems, and thus they need to be dealt with, both on the environmental front (clean, clean, clean!) and on the over-the-counter medication front.