red conjunctiva. You may also notice that the patient has developed dark circles underneath the eyes due to venous stasis, often referred to as “allergic shiners.”

Numerous medications are associated with drug-induced rhinitis. The most frequently incriminated agents are antihypertensive medications. Table 1 lists some of the common medication-related causes of rhinitis. Illicit drugs, such as cocaine, have also been associated with rhinitis, due to nasal irritation and inflammation.

ASTHMA COMORBIDITY

Probably the most significant comorbidity of allergic rhinitis is asthma, a condition involving chronic inflammation of the airways.

The presence of wheezing is a key symptom indicator for asthma, although the absence of wheezing does not exclude the possibility of asthma. Other key symptom indicators include a history of cough (particularly at night), recurrent difficulty breathing or recurrent chest tightness. These symptoms are often worsened in the presence of exercise, viral infection, inhaled allergens or irritants, changes in weather, strong emotional expression, stress or menstrual cycles. Although the presence of these indicators increases the probability of asthma, spirometry is essential to establish the diagnosis.

ENVIRONMENTAL CONTROL

Intermittent allergic rhinitis is commonly caused by allergies to seasonal pollens, outdoor molds or occupational irritants. Persistent allergic rhinitis is typically caused by allergies within the home or work, or outdoor allergies that are present year-round (Table 2). Most environmental modifications involve the control of indoor allergens.

Dust mites are commonly found in bedding, carpets, upholstered furniture, curtains and soft toys. Dust mites are microscopic insects that thrive in warm, humid places. Avoidance of these mites can be accomplished by using plastic dust mite covers on pillows and mattresses. To avoid dust mites, the World Allergy Organization recommends washing bedding, including pil-

lows and duvets, every one to two weeks at 55 to 60 degrees Celsius. Soft toys can also be washed at 55 to 60 degrees Celsius or put in the freezer to kill mites. Dust mites can also be killed by exposing mattresses, rugs and carpets to direct strong sunlight for more than three hours. Other recommendations to reduce dust mites include sufficient ventilation to decrease humidity, use of a dehumidifier or HEPA filter in the bedroom and removal of carpeting in the bedroom.

Mold is common in basements, bathrooms, plants and old newspapers. To reduce exposure to mold indoors, carpeting, wallpaper and houseplants should be removed from the bedroom or household. The use of a dehumidifier is recommended if the relative humidity is consistently above 50 percent. Appropriate maintenance of ventilation and air-conditioning systems is essential for reducing mold spores. Firewood should be stored outside because mold can be present in the bark of the wood. Piles of old newspapers should not be stored in the house. For contaminated surfaces, a 5 percent ammonia solution is useful for removing mold.

When pet owners are found to be allergic to pet dander, pets should be sent to an alternative home if possible. If pet owners can not bear to part with them, attempts should be made to control dander. Pet dander can remain in household dust for several months after the animal has left. Cat dander can remain airborne for six hours. Frequent pet shampoos, house cleaning utilizing a HEPA vacuum, removal of carpets and applying special sprays that help control pet shedding may help control symptoms. Pets should also be kept out of bedrooms or be kept outside.

Outdoor allergens can be avoided by closing car and home windows, as well as limiting outdoor activities during high pollen season or at peak hours (usually between 5 a.m. to 10 a.m.). When outdoor activities are necessary, wearing glasses or sunglasses may prevent pollen from entering the eyes. Patients can also consider wearing a mask over the nose and mouth to prevent inhalation of pollen. Air conditioners, with frequently changed filters, may also be helpful to decrease humidity and filter out

mites, mold, pollen and dander.

OVER-THE-COUNTER TREATMENT

A wide variety of treatment options are available for the treatment of allergic rhinitis. Many of these medications are available without a prescription.

Oral antihistamines

Antihistamines have been used to treat allergic rhinitis for many decades. By blocking histamine at the H1 receptor, they relieve the early-stage symptoms caused by histamine. These include itching, sneezing, rhinorrhea and allergic conjunctivitis. However, antihisaminesantihistamines have little effect on nasal congestion. Antihistamines are more effective in preventing the actions of histamine than they are at reversing the effects of histamine.

Antihistamines are classif ied as either f irst generation or second generation. The agents in these two classifications are differentiated by their selectivity for the H1 receptor and by their ability to cross the blood brain barrier. Both classes of antihistamines are effective for long-term treatment and prevention of allergic rhinitis.

First generation antihistamines are available without a prescription and include such familiar agents as diphenhydramine (Benadryl), chlorpheniramine ( Chlor-Trimeton), brompheniramine and carbino-xamine maleate. These agents easily cross the blood brain barrier, leading to significant sedation, drowsiness and dizziness. They also block cholinergic receptors, which in turn can cause urinary retention, dry mouth, dry eyes, blurred vision and constipation. In young children, first generation antihistamines can cause excitation rather than sedation. First generation antihistamines should not be recommended to patients who have narrow-angle glaucoma, benign prostatic hypertrophy or bladder neck obstruction.

Patients using first generation antihistamines should not use alcohol or other central nervous system depressants while they are taking antihistamines. Until patients know how they will react to an antihistamine, they should use caution operating