Hay fever is a leading cause of missed work days and poor productivity.

An estimated 55 percent of employees reported experiencing hay fever symptoms for an average of 52.5 days, according to a study published in Current Medical Research and Opinion. They were absent an average of 3.6 days per year due to allergies, and were unproductive 2.3 hours per workday when they experienced symptoms.

That results in an estimated cost of more than $601 million in total lost productivity annually, according to a study in the American Journal of Managed Care.

Why the poor performance? Allergies don’t just cause sniffling and sneezing, which most people can ignore. They can cause sore throats, headaches, sinus infections, itchy eyes, fatigue and general malaise—symptoms that make it difficult to tough it out.

But experts believe that people with allergies don’t have to suffer quite as much as they do. Many people don’t treat their allergies as aggressively as they could be. Here’s what you need to do to reduce your symptoms and increase your productivity at work:

1. Start taking meds–now. Some people wait until the symptoms build up to the point of distraction before they start taking their allergy medications.  But as symptoms worsen, they become more difficult to treat, and can lead to complications like sinusitis. In addition, nasal steroid sprays take 5 to 7 days to quell your inflammatory response. It can prevent sneezing and congestion if started early, says allergist Dr. Dean Mitchell, author of The Allergy and Asthma Solution.

Start taking allergy medications a few weeks before allergy season hits (this year, spring has come early so you’ll need to start right away).

2. Don’t quit your meds.  Nasal sprays can take several days to reach their full effect, so don’t assume they’re not working if you don’t get relief right away. Make sure you stick with it for at least a week. And don't stop using nasal sprays once your symptoms are under control, because your allergies will just return. If symptoms do get worse or your over-the-counter nasal sprays are not working, ask your doctor to write a prescription for a nasal cortisone spray.

3. Take an antihistamine at night. The older OTC antihistamines (like Benadryl) are stronger than newer drugs, but they make you drowsy. That makes them perfect for nighttime use.

4. Don’t forget your eyes.  Use a prescription antihistamine eye drop as soon as you feel mild itching. Avoid OTC decongestant eye drops because they can cause rebound redness when you stop using them.

Laurie Tarkan is an award-winning health journalist whose work appears in the New York Times, among other national magazines and websites. She has authored several health books, including "Perfect Hormone Balance for Fertility." Follow her on Twitter and Facebook.