Use the medication prescribed by your physician. Medications for allergic and nonallergic rhinitis fall into four categories.

Antihistamines lessen symptoms of hay fever and other allergies.

• To reduce stomach irritation, take medicine with food or a glass of milk.
• Antihistamines can be used on an "as needed" basis.
• Don't take antihistamines with grapefruit juice.
• Don't crush, break, or chew extended-release tablets. Swallow them whole.
• If you must take this medicine regularly, and you miss a dose, take it as soon as possible. However, if it is almost time for you to take your next scheduled dose, take that dose and do not take the missed dose.
• Don't drink alcohol or take any other medicines that make you sleepy.
• Don't drive or do dangerous jobs if this medicine makes you sleepy.
• Take these medications as directed.

• Drowsiness (some newer antihistamines do not cause drowsiness)
• Thickening of mucus
• Dry mouth

Decongestants treat symptoms of allergies, colds or flu, such as a stuffy or runny nose, sneezing or sinus congestion. There are many over-the-counter medications for nasal symptoms and the common cold. These may combine antihistamines with decongestants or contain decongestants alone.

• Avoid nasal decongestant sprays. While these medications offer temporary relief, they can result in ongoing obstruction of the nasal passage. They shrink the nasal mucous membranes briefly, and when the effect of the medication ends, the membranes once again swell. This swelling becomes greater with repeated use, and finally the nose becomes severely obstructed.
• If you must take this medicine regularly, and you miss a dose, take it as soon as possible. However, if it is almost time for you to take your next scheduled dose, take that dose and do not take the missed dose.
• Do not drink alcohol or take any other medicines that make you sleepy.

Serious side effects rarely occur when this medication is taken as recommended. However, decongestants are stimulant drugs and may:

• Aggravate high blood pressure.
• Cause your heart to beat differently.
• Cause difficulty with urination. (If this occurs, it is most often in older men.)

Cromolyn (Nasalcrom) is a nasal spray that is available without a prescription. It is a preventive type of medication — it prevents inflammation and can relieve the symptoms of allergic rhinitis, but not those of nonallergic rhinitis. To be most effective, it should be started before the beginning of the allergy season. In some people, it causes stinging or burning in the nose.

These are effective in both allergic and nonallergic rhinitis and can be given by injection, pill or spray.

• When taking the medication by mouth, take it with an antacid or food.
• If you have a personal or family history of diabetes or high blood pressure, it's very important for your blood sugar and blood pressure to be monitored while you are receiving the medication.

When used in pill form or by injection, cortisone may have serious side effects, particularly when used over long periods of time. The side effects of cortisone-containing drugs always must be weighed against the seriousness of the allergic symptoms. Some of the common side effects of corticosteroids include:

• Insomnia
• Increased energy, euphoria
• Swelling of feet and legs
• Mood swings
• Increased appetite
• Yeast (fungal) infections
• Stomach irritation (gastritis, ulcers)
• High blood sugar levels
• Muscle weakness
• Easy bruising

Corticosteroid nasal sprays don't cause the same serious side effects as the pills or injections. However, they can irritate the nose and cause stinging, burning and minor bleeding. A small percentage of people must stop the medication because of nosebleeds. Corticosteroid nasal sprays work slowly and must be prescribed by your physician.

New medications are being tested and put on the market continuously. Ask your physician about new medications for treating your condition.

If you have questions or concerns about your medications, discuss them with your physician. Other possible side effects of these medications are not listed here because they occur infrequently. Discuss concerns you may have with your physician. If you have any unusual reactions that you believe are caused by your medication, contact a member of your health-care team.