Seasonal allergies are estimated to affect somewhere in the neighborhood of 20 million people in the U.S. Those who are affected can tell you just how miserable the condition can make people feel. For many people, the winter months mean a break from symptoms, but for others, the trouble has just begun.

Allergic rhinitis and hay fever are two other terms that are used interchangeably with the term seasonal allergies. While it is not known exactly why seasonal allergies occur, science is starting to uncover some of the mechanisms for allergies. There is a definite genetic component to allergies, as someone with an allergic parent is more likely to develop allergies himself.

An allergy is caused by the activation of the immune system when a person is exposed to the allergen or foreign invaders. The immune system normally senses foreign invaders and correctly attacks and destroys them - this is our means of protecting our bodies from infection. However, when someone has an allergy, the immune system overreacts and attacks too hard and for too long, causing symptoms whenever the person is exposed to the allergen or foreign invaders.

The symptoms of allergic rhinitis can vary from one person to the next but include nasal itching, serial sneezing, runny nose and nasal as well as sinus congestion. In addition, the eyes can become irritated, itchy, watery and red. There may also be associated coughing. Many people with allergies also seem to suffer from asthma and the same thing that triggers an attack of someone's allergies may also precipitate an attack of asthma.

The most commonly identified allergies are to pollen (which may be in the form of ragweed, grass or tree pollens), molds, animal hair and dust mites. With pollen and mold allergy, the winter usually brings relief of symptoms. However, if you live in a climate where it is warm year-round, the winter may not provide any relief (in which case your allergies are called perennial instead of seasonal).

Those who have allergies to pets and live in a four-season climate may find that the winter makes things worse, as pet and owner are forced into the house more frequently due to the cold. It's always harder to get the cat or dog to go outside when the temperature outside is ten below zero. Dust mites are usually found running rampant in the bedroom, so those who tend to sleep more when its cold and dark outside are advised to go out and buy special dust covers for their pillows and mattresses. Otherwise, it could be a long winter, indeed.

Cigarette smoking often aggravates (or may even be a cause of) allergy symptoms. Those who live with a smoker may notice worsening of their symptoms during the winter because the smoker is no longer willing to smoke outside or open the windows when it is cold out. This can be especially problematic for children, who have little authority to demand that the smoker of the house cease and desist.

The other problems in the winter for some seasonal allergy sufferers are infections. Viral respiratory infections like the flu and the common cold run rampant in the winter and can aggravate allergic symptoms. Getting an annual flu shot, washing your hands frequently and avoiding exposure to sick people can help reduce this problem.

Treatment of seasonal allergies is the same whether symptoms are worse in the summer or winter. The mainstay of therapy is still antihistamine, which are enough to relieve symptoms in many people. Over-the-counter preparations are available, but tend to cause drowsiness. Newer, less sedating antihistamines are available by prescription from your doctor. Other treatments are also available - check with your health care provider.

So while many with seasonal allergies cheer the first snowfall, others know that their suffering is just about to begin. Those who live in hot or tropical climates, or are allergic to animal hair, dust mites, or other indoor objects get no relief from the coming of the winter season. Avoiding your trigger is still the best prescription we have, though it is not always possible - especially if that trigger is barking at the back door to come in out of the cold.