An allergy is an inappropriate reaction of the body to a normally harmless substance. When the body comes into contact with a potential invader, the immune system mounts a defense. An antibody is developed to recognize and attack the substance the next time it is encountered. The body develops an antibody against each trigger of an attack (called allergens). Some of the most common allergens are pollen, mold, dust mites and animal dander.

Respiratory allergies, also called allergic rhinitis, cause a variety of symptoms. The most common signs include sneezing, coughing, runny or clogged nose, itching or watery eyes, nose or throat and red or watery eyes.

According to the American Academy of Allergy, Asthma and Immunology about 35.9 million people have seasonal allergic rhinitis (i.e., allergy symptoms that occur predictably at certain times of the year). The condition causes 14.1 million visits to physicians and $6 billion for treatments.

Treating Allergies

There are several different types of treatment for respiratory allergies. Antihistamines are drugs that counteract the body's production of histamine, which occurs in response to contact with an allergen. They are available as over-the-counter and prescription products and can help prevent or reduce many of the signs of allergy. Decongestants are sometimes added to antihistamines to relieve nasal congestion and help the sinuses drain. Prescription eye drops with antihistamines help reduce eye itching, tearing and burning.

Steroid sprays are inhaled through the nose to reduce inflammation, nasal swelling and congestion. Another nasal spray, cromolyn sodium, prevents inflammation that can cause nasal congestion.

Patients with more severe allergies may consider immunotherapy. Doctors start by giving very minute amounts of an allergen. The initial dose is so small it hopefully won't trigger a reaction by the body. As the body becomes accustomed to the allergen, the dose is gradually increased. Eventually, patients' bodies learn to accept "normal" levels of the allergen without reacting to the substance.

Making the Most of Your Allergy Medicines

Our body follows a natural clock, called the circadian rhythm. Various body functions, like blood pressure and body temperature rise and fall in response to these rhythms.

Circadian rhythms can also influence symptoms of disease. Richard Martin, M.D., Pulmonologist with National Jewish Medical and Research Center, says, in the case of allergies, most patients experience their worse symptoms in the early morning hours, generally from 4:00 am to 6:00 am. By the time a person gets out of bed, takes allergy medicine and allows time for the medication to take effect, the symptoms have already passed.

Martin says people who have peak allergy symptoms in the early morning hours should take their allergy medications at night, just before going to bed. Taking the medicine at night ensures there will be enough levels of the drug in the bloodstream to reduce or prevent onset of symptoms when waking up in the morning.

For general information on allergies:

American Academy of Allergy, Asthma and Immunology

Asthma and Allergy Foundation of America

National Institute of Allergy and Infectious Diseases

National Jewish Medical and Research Center