Allergic asthma

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Asthma is a breathing disorder characterized by inflammation of the airways and recurrent episodes of breathing difficulty. These episodes, sometimes referred to as asthma attacks, are triggered by irritation of the inflamed airways. In allergic asthma, the attacks occur when substances known as allergens are inhaled, causing an allergic reaction. Allergens are harmless substances that the body's immune system mistakenly reacts to as though they are harmful. Common allergens include pollen, dust, animal dander, and mold. The immune response leads to the symptoms of asthma. Allergic asthma is the most common form of the disorder.

A hallmark of asthma is bronchial hyperresponsiveness, which means the airways are especially sensitive to irritants and respond excessively. Because of this hyperresponsiveness, attacks can be triggered by irritants other than allergens, such as physical activity, respiratory infections, or exposure to tobacco smoke, in people with allergic asthma.

An asthma attack is characterized by tightening of the muscles around the airways (bronchoconstriction), which narrows the airway and makes breathing difficult. Additionally, the immune reaction can lead to swelling of the airways and overproduction of mucus. During an attack, an affected individual can experience chest tightness, wheezing, shortness of breath, and coughing. Over time, the muscles around the airways can become enlarged (hypertrophied), further narrowing the airways.

Some people with allergic asthma have another allergic disorder, such as hay fever (allergic rhinitis) or food allergies. Asthma is sometimes part of a series of allergic disorders, referred to as the atopic march. Development of these conditions typically follows a pattern, beginning with eczema (atopic dermatitis), followed by food allergies, then hay fever, and finally asthma. However, not all individuals with asthma have progressed through the atopic march, and not all individuals with one allergic disease will develop others.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

The cause of allergic asthma is complex. It is likely that a combination of multiple genetic and environmental factors contribute to development of the condition. Doctors believe genes are involved because having a family member with allergic asthma or another allergic disorder increases a person's risk of developing asthma.

Studies suggest that more than 100 genes may be associated with allergic asthma, but each seems to be a factor in only one or a few populations. Many of the associated genes are involved in the body's immune response. Others play a role in lung and airway function.

There is evidence that an unbalanced immune response underlies allergic asthma. While there is normally a balance between type 1 (or Th1) and type 2 (or Th2) immune reactions in the body, many individuals with allergic asthma predominantly have type 2 reactions. Type 2 reactions lead to the production of immune proteins called IgE antibodies and the generation of other factors that predispose to bronchial hyperresponsiveness. Normally, the body produces IgE antibodies in response to foreign invaders, particularly parasitic worms. For unknown reasons, in susceptible individuals, the body reacts to an allergen as if it is harmful, producing IgE antibodies specific to it. Upon later encounters with the allergen, IgE antibodies recognize it, which stimulates an immune response, causing bronchoconstriction, airway swelling, and mucus production.

Not everyone with a variation in one of the allergic asthma-associated genes develops the condition; exposure to certain environmental factors also contributes to its development. Studies suggest that these exposures trigger epigenetic changes to the DNA. Epigenetic changes modify DNA without changing the DNA sequence. They can affect gene activity and regulate the production of proteins, which may influence the development of allergies in susceptible individuals.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

Allergic asthma can be passed through generations in families, but the inheritance pattern is unknown. People with mutations in one or more of the associated genes inherit an increased risk of allergic asthma, not the condition itself. Because allergic asthma is a complex condition influenced by genetic and environmental factors, not all people with a mutation in an asthma-associated gene will develop the disorder.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Approximately 235 million people worldwide have asthma. In the United States, the condition affects an estimated 8 percent of the population. In nearly 90 percent of children and 50 percent of adults with asthma, the condition is classified as allergic asthma.

Which doctor should you see?

The suggested department for discussing Allergic asthma is Pulmonology, with a pulmonologist / chest physician as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• What is the likely explanation for the breathing symptoms?
• Would a breathing test or another investigation change management?
• If symptoms worsen, what written action plan should be followed?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Allergic asthma. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.