Physiological factors that may trigger or increase asthma symptoms include:

• Viral upper respiratory infections.
• Exercise.
• Untreated conditions such as rhinitis, sinusitis, and gastroesophageal reflux.
• Drugs such as aspirin and other anti-inflammatory drugs.
• Stress and strong emotions.

There are many allergens and irritants that can cause an asthma sufferer to experience an episode. Common indoor environmental irritants and allergens include:

• Pet fur or feathers, urine, saliva and dander.
• House-dust mites.
• Cockroach waste and decomposing carcass.
• Mold and mildew spores.
• Tobacco smoke and wood smoke.
• Perfumes and hairsprays.
• Cleaning solutions, pesticides and paints.

Common outdoor environmental irritants and allergens include

• Pollen from trees, grasses, and weeds.
• Mold and mildew spores.
• Changes in humidity.
• Exposure to cold air.
• Industrial emissions and other air pollutants.

Common Environmental Allergens

The cause of the underlying airway inflammation in patients with asthma is unknown. Once a person has inflamed airways and asthma, environmental triggers can cause or increase asthma symptoms.

Common indoor allergens and asthma triggers include:

• Pet fur or feathers, saliva, urine and dander.
• House-dust mites.
• Cockroach waste and dust from decomposed carcasses.
• Indoor mold and mildew spores.
• Tobacco smoke and wood smoke.
• Cleaning solutions, paint, and pesticides.
• Perfumes and hairspray.

Common outdoor allergens and asthma triggers include

• Pollen from trees, grasses, and weeds.
• Outdoor mold and mildew spores.
• Changes in humidity.
• Exposure to cold air.
• Industrial emissions and other air pollutants.

Exposure to chemicals or airborne pollutants at work can trigger asthma. In some cases of work-related asthma a single, high-dose exposure to ammonia, chlorine gas, or hydrochloric acid can cause the onset of asthma. Work-related or aggravated asthma can also result from long-term, continuous exposures to some chemicals.

Allergy Testing

Since allergies can be an important factor in causing asthma symptoms, the diagnosis of asthma often includes testing for common environmental allergens, such as house-dust mites, molds, animal dander, cockroaches, and pollens.

Patients with persistent asthma should be tested for sensitivity to the allergens they are routinely exposed to. Testing helps diagnose allergic factors that contribute to asthma symptoms and severity. Once allergens are identified that cause asthma symptoms, exposure to those allergens can be controlled.

How to Avoid Triggers

Dust Mites - Live and breed in mattresses, bed linens, carpet, stuffed toys, fabric-covered furniture, etc and can be found in every home. They resemble a flea, but are so small that a microscope is needed to see them. To reduce asthma symptoms associated with dust mites, here are some ways to reduce exposure in the home:

• Wash sheets and blankets in hot water, once a week.
• Choose stuffed toys that are washable. Wash them in hot water and dry thoroughly periodically. Stuffed toys should not be placed on beds.
• Cover mattresses and pillows in dust-proof (allergen-impermeable) zipped covers.

Pets - To help avoid an asthma episode brought on by a pet, here are some suggestions:

• Consider keeping pets outdoors or even finding a new home for your pets especially if asthma episodes induced by exposure to the pet are severe.
• Make the bedrooms and other sleeping areas of those with asthma off limits to pets at all times, and keep the door closed.
• Keep indoor pets away from fabric-covered furniture, carpets and stuffed toys. Vacuum, dust and clean often.

Molds and Mildew - Grow in damp and shady places. To help avoid an asthma episode triggered by molds and mildew try these strategies:

• Wash mold off hard surfaces and dry completely. Absorbent materials, such as ceiling tiles and carpet with mold, may need to be replaced.
• Locate the source of moisture - drainage problem, leaky plumbing, poor ventilation, etc. and have the problem corrected.
• Keep drip pans in your air conditioner, refrigerator and dehumidifier clean and dry.
• Use exhaust fans or open windows in kitchens and bathrooms when showering, cooking or using the dishwasher.
• Maintain low indoor humidity, ideally between 30 to 50 percent relative humidity. Humidity levels can be measured by hygrometers, which are available at local hardware stores.

Pests - Droppings or decaying body parts of pests such as cockroaches or rodents can be asthma triggers. To help avoid an asthma episode, these measures can be taken to keep them out of your home:

• Do not leave food or garbage out.
• Store food in airtight containers.
• Clean all food crumbs or spilled liquids right away.
• Try using poison baits, boric acid (for cockroaches) or traps first before using pesticide sprays. Tobacco Smoke - Asthma can be triggered by the smoke from a cigarette, pipe or cigar, as well as the secondhand smoke that is exhaled by other smokers.
• Set a 'no smoking' policy for your home and car.
• Avoid going into homes and businesses where tobacco smoke is present. Perfumes/Fragranced Products - Products that have strong odors such as perfumes, hairsprays, paints, and cleaning products can cause an asthma episode.
• Avoid using perfume or heavily scented products.
• Ventilate well when using scented hairsprays or cleaning products inside the house.
• Store paints and other highly scented products in the garage. Make sure containers are properly sealed. When painting, make sure the room is well ventilated.

Exercise - Physical exertion can cause some people to have an asthma attack. An episode can occur during or after exercise.

• Talk to your doctor about medicines available to prevent an attack during exercise. With proper medications, asthma sufferers can live healthy, active lives.
• Choose an exercise that is less likely to trigger your asthma, like swimming, walking or leisure biking.

Cold Air - Can also trigger an asthma attack. Take these precautions during cold weather:

• Avoid going out on extremely cold days.
• Wear a scarf around your mouth when you go outside.