What to know about intrinsic and extrinsic asthma

Intrinsic and extrinsic asthma are two subtypes of asthma, which people more commonly refer to as allergic and nonallergic asthma.

Both types cause the same symptoms. The difference between the two subtypes is what causes and triggers asthma symptoms. The treatments are similar for each type, although the prevention strategies differ.

Triggers

In people with extrinsic asthma, allergens trigger respiratory symptoms. Common triggers for extrinsic asthma include:

• pollen
• mold
• dust mites
• pet dander

In some cases, a person is allergic to more than one substance, and several allergens trigger asthma symptoms.

In people with intrinsic asthma, allergies are not responsible for the symptoms. Instead, the following triggers may cause symptoms:

• cold
• humidity
• stress
• exercise
• pollution
• irritants in the air, such as smoke
• respiratory infections, such as colds, the flu, and sinus infections

In some cases, intrinsic asthma can occur with no known cause.

Prevalence

Extrinsic or allergic asthma is the most common form of the disease. About 60-90% of people with asthma have allergic asthma.

Intrinsic or nonallergic asthma is less common, occurring in anywhere from 10% to 40% of people with asthma.

It occurs more often in females than males and typically develops later in life than extrinsic asthma.

Causes

In all types of asthma, a person has overly sensitive airways and airway inflammation, which produces asthma symptoms.

Inflammation causes swelling in the airways that narrows the tubes and makes breathing difficult. The body also produces excess mucus, which further impairs breathing. These factors decrease the amount of air that can get into the lungs.

The inflammatory processes are similar in extrinsic and intrinsic asthma. Airway biopsies have demonstrated that inflammation in asthma generally involves the same cells that play prominent roles whether the individual is allergic or not. This supports the belief that the consequences of mast cell activation mediated by a variety of cells are key to the development of clinical asthma.

Research has also found that there may be more similarities between the two types of asthma than researchers previously thought. Both types of asthma involve the production of IgE locally in the airways in response to the relevant triggers.

Extrinsic asthma occurs when the immune system overreacts to a harmless substance, such as pollen or dust. The body releases an antibody called immunoglobin E (IgE). The release of this antibody leads to inflammation and asthma symptoms.

Intrinsic asthma occurs when something other than allergens triggers an immune system response. The body then releases IgE. People are not always able to identify the trigger.

The symptoms of extrinsic and intrinsic asthma are the same and may include:

• wheezing
• chest tightness
• shortness of breath
• coughing
• increased mucus production
• trouble breathing

Symptoms can vary in severity and may develop suddenly. Ignoring the signs and symptoms of an asthma attack can lead to a life-threatening situation. Recognizing symptoms as soon as possible and following an asthma action plan can help decrease the severity of an attack and reduce complications.

The treatment options for intrinsic and extrinsic asthma are similar and include medications, lifestyle changes, and the avoidance of triggers. Since the triggers are different, the prevention strategies may differ.

Reducing triggers

It may be easier to identify the triggers for extrinsic asthma because allergies are the culprit. With both types of asthma, the identification of triggers allows an individual to take steps to reduce exposure and decrease symptoms.

The following steps can help reduce asthma symptoms in people with extrinsic asthma:

• fixing leaky pipes to prevent mold buildup
• keeping doors and windows closed when the pollen count is high
• vacuuming often to reduce dust
• keeping pets out of the bedroom

Triggers of intrinsic asthma do not involve a specific allergen. Due to the variability of triggers, it can take a little longer to determine the cause of flare-ups. People may find that avoiding humid, dry, or cold weather can prevent symptoms.

Medications

People can use the following medications to treat flare-ups of both intrinsic and extrinsic asthma:

Short-acting bronchodilators

Short-acting bronchodilators, also called quick relief medications, reduce symptoms fast. They work by relaxing the muscles of the airways.

Long-acting medications

People take long-acting bronchodilators daily, and they also open up the airways. Long-acting bronchodilators do not treat sudden symptoms as they take longer to work than short-acting bronchodilators.

Corticosteroids

Corticosteroids decrease inflammation in the airways. People usually take daily inhaled steroids to control asthma symptoms and will take oral steroids for an acute flare of their asthma

Omalizumab

Omalizumab is an anti-IgE antibody therapy that prevents the release of IgE. Reducing IgE decreases the allergic response and prevents asthma symptoms.

People usually use omalizumab to treat extrinsic asthma, but it may also help with intrinsic asthma.

Lifestyle changes

Lifestyle changes might also help decrease symptoms of both types of asthma.

People with asthma may wish to consider adopting the following lifestyle practices:

• maintaining a healthy weight
• quitting smoking
• avoiding secondhand smoke
• reducing stress
• getting a flu vaccine each year
• washing the hands frequently to decrease the risk of infection

Although there is currently no cure for either extrinsic or intrinsic asthma, people can manage the symptoms with medications, prevention methods, and lifestyle changes.

Intrinsic asthma is often harder to control than extrinsic asthma, as identifying its triggers is sometimes difficult. People can work closely with a doctor to determine the causes of asthma symptoms and find an effective treatment.