Asthma and Your Immune System

The same system that helps protect you from infections—your immune system—can also be responsible for your worsening asthma. You may notice that at the same time you have that runny nose, watery eyes, and sinus congestion, your peak flows are lower, you're wheezing more, and you may experience more shortness of breath. So how are your immune system and asthma linked? Can you do anything to keep your immune system from making your asthma worse?

The immune system normally protects you against foreign bacteria and viruses. In asthma and other allergic diseases, the immune system may be the cause of your worsening symptoms.

Asthma and Allergies Often Go Hand in Hand

Many asthmatics are atopic, meaning they have an inherited predisposition toward developing allergies. Allergies occur when your immune system develops an exaggerated response to certain foreign substances or allergens.

The Allergic Cascade: Your Body's Response to Allergens

With allergies, your body's immune system senses these allergens, perceives them as foreign, and begins to prepare to fight them off as a foreign intruder. The process that takes place is often referred to as the allergic cascade, which generally occurs in these three steps:

1. Sensitization
2. Early phase response
3. Late phase response

Sensitization: The First Phase of the Allergic Cascade

The first time you're exposed to an allergen, this is called sensitization and you will not usually have symptoms.

You may be exposed to allergens that stimulate the allergic cascade through:

• Inhalation of substances such as dander, pollen, or dust mites where the substances bind to membranes in your lungs
• Ingestion of foods or medicines where the initial immune system reactions occur in the stomach
• Physical contact of your skin with substances such as poison ivy

Immunologically, your body senses the allergen as foreign and sets off a cascade of events stimulating several different types of immune cells:

• T cells rapidly stimulate B cells
• B cells transform into plasma cells
• Plasma cells produce IgE antibodies specific to the allergen
• Immunoglobulin E (IgE) antibodies bind to mast cells

At this point, the allergen has triggered the allergy cascade, but you will not develop any symptoms or even realize that anything has happened. However, during subsequent exposures to the allergen, you may develop asthma symptoms as part of the early-phase response.

Early Phase Response: The Second Phase of the Allergic Cascade

With re-exposure to the allergen. your immune system senses the allergen as foreign, which leads to the following:

• The mast cell/IgE complexes produced in the sensitization phase bind to the allergen thinking that it's a foreign invader such as bacteria or a virus
• The mast cells then release inflammatory cells called mediators, such as histamine, that quickly travel throughout your body with the purpose of fighting off the foreign invaders
• You begin to experience symptoms of your body’s overreaction to the allergen

The mediators react in different parts of your body causing your allergy symptoms.

You may begin wheezing, coughing, or feeling short of breath as the immunologic response causes swelling and narrowing of the airways in your lung. You may only experience a runny nose or watery, itchy eyes. The immunologic response begins nearly immediately with symptoms occurring very shortly after re-exposure and lasting 3-4 hours.

Late Phase Response: The Third Phase of the Allergic Cascade

The late phase response begins at the same time as the early phase response but doesn't cause symptoms for several hours. Mediators released by the re-exposure to an allergen also stimulate other kinds of immune cells called eosinophils.

Eosinophils contain substances that when released normally fight off infections, but in asthma, the cells damage the lungs causing more inflammation and worsening symptoms.

In the late phase, symptoms will not develop for at least 4 hours but they may last as long as 24 hours. Increased inflammation and obstruction of the airflow may be more severe than what is seen during the early phase.

Understanding the Allergic Cascade

The most obvious approach to treating the allergic cascade would be to avoid the allergens altogether and prevent it from occurring. While this may work for some allergens like specific foods and pet dander, other allergens such as dust and molds may be more difficult and medications are often needed.

You need to develop a list of your asthma triggers as they generally will start the cascade. Additionally, you need to make sure that you know what it means to have poor asthma control. Using your rescue inhaler more than two times per week or waking up with asthma symptoms more than twice per month means your asthma isn't well-controlled. When you have identified your asthma triggers you need to make sure that you avoid mistakes like allowing pets to be in your bedroom or sleeping with the window open.

Treatments for Asthma and Allergies

Current therapies for asthma and allergies generally target specific parts of the allergic cascade. First generation antihistamine drugs like diphenhydramine (Benadryl) or second-generation antihistamines like loratadine (Claritin) or cetirizine (Zyrtec) prevent allergy symptoms by inhibiting the inflammatory response of the mediators released during the early phase of the allergic cascade.

Antihistamines prevent mediators, such as histamine, from binding to receptors in the nose and eyes that cause the allergic symptoms of sneezing, runny nose, congestion, and watery eyes. It's important for you to document or at least be aware when taking an antihistamine if it improves your asthma control and symptoms. One good idea is to note when you take the antihistamine and see if it objectively decreases your rescue inhaler use or if you just feel better.

Bronchodilators such as albuterol target the early phase of asthma, causing a widening of the airways and relief of airway obstruction and making it easier to breathe. Drugs with anti-inflammatory properties, such as steroids and leukotriene antagonists, may be used acutely to decrease the late phase response or used as a preventive measure to attempt to keep the late phase response from occurring at all.

Finally, allergy shots or immunotherapy may be used in an attempt to desensitize a patient to an allergen. With the shots, your body decreases its foreign invader response—the immune system generates less IgE and hopefully does not react as strongly to a particular allergen.

It's Important to Take Medications Correctly

These medications need to be taken every day to be effective and will not work if you try to take them on an as-needed basis. Whether you're using your rescue inhaler or a controller inhaler, you need to spend time making sure your inhaler technique is correct. If you don't have the correct technique, not all of the medication will get into your lungs.

A Word From Verywell

Hopefully, a better understanding of your immune system will give you a better understanding of what might cause your asthma symptoms to worsen and help you gain better control.

_Sources:

Asthma and Allergy Foundation of America (AAFA). Allergens and Allergic Asthma. Updated September 2015.

Delves, PJ. Overview of Allergic Reactions. Merck Manual: Consumer Version. 

National Heart, Lung, and Blood Institute. Expert Panel Report 3 (EPR3): Guidelines for the Diagnosis and Management of Asthma. Published August 28, 2007.