Nasal Allergy Medications (cont.)

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Antihistamines perform best when taken regularly or before an allergic reaction begins. The second generation antihistamines may take up to an hour or more to become effective. They should be taken well before an expected allergic exposure, such as a visit to a friend who has a cat, and that the person may be allergic to cat dander.

What are common side effects of antihistamines?

Since the first generation antihistamines can penetrate the brain tissue, they generally cause more side effects than the second generation drugs, which usually cannot enter the central nervous system. Drowsiness is the most noticeable side effect, but this is sometimes desirable. For example, it may be useful when nighttime symptoms prevent restful sleep. During the day, however, this effect can cause problems.

Be cautious about driving a car or operating a machine when using OTC antihistamines. Do not take any tranquilizers or drink alcohol along with these drugs. The combination may promote more drowsiness. Also, a person should check with the doctor before taking an antihistamine if they have glaucoma or thyroid, heart, or prostate problems because the antihistamines may make these problems worse.

The first generation antihistamines may also cause troublesome anticholinergic effects such as heart palpitations, difficulty urinating, constipation, dry mouth, and nervousness. These side effects usually occur when the medication is taken at higher than recommended doses.

The second generation of antihistamines currently on the market has few, if any, significant side effects at the recommended doses.

Antihistamines may be used for nasal symptoms in patients with asthma. It was previously thought that these drugs would dry up the airways in the patient's bronchial tubes and aggravate the asthma. However, there is no good evidence supporting this notion. Improving nasal allergy symptoms may benefit patients with asthma.

What are decongestants?

Nasal stuffiness or congestion occurs as a result of swelling of the nasal membranes. Histamine opens the blood vessels and encourages fluid leakage from them, thereby causing the tissues to become "congested." This reaction reduces the space inside the nose through which we breathe and results in the typical "blocked" or stuffy nose. While antihistamines can control many symptoms of allergic rhinitis, they are not very helpful for treating nasal congestion once it has already occurred. At this point, decongestants can be a very useful addition (see next section).



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