When you come in contact with something you’re allergic to, your mast cells open up, spilling out histamine and triggering the symptoms we associate with an allergic reaction: stuffy or runny nose, itchy eyes and sinus pressure.Because they work by preventing histamine from escaping from your mast cells, antihistamines work best if you take them at least 1 hour BEFORE being exposed to what sets your allergies off.
This drying action can actually help relieve your runny nose and watery eyes.
If Claritin®, Allegra® or Zyrtec® aren’t giving you enough relief, you can try one of the older sedating antihistamines.
The most powerful is Benadryl® also known as diphenhydramine.
It’s more likely to cause you some drowsiness compared to Claritin® or Allegra® but because it’s more drying than either of them it can help dry up your runny nose.
You only have to take it once a day and it causes minimal drowsiness.