Atopy

What is Atopy?

Atopy is a condition that makes a person’s immune system more likely to react to a range of allergens or foreign substances, which results in an excess production of a type of antibody called immunoglobulin E (IgE). This can cause allergic reactions. Common symptoms of atopy include conditions like asthma, hay fever (allergic rhinitis), eczema (atopic dermatitis), and food allergies. It’s possible for someone to experience two or more of these conditions at the same time or at different points in their life.

Atopy can also be linked with other conditions like eye allergy (allergic conjunctivitis), certain drug allergies, reactions to insect bites, hives (urticaria), swelling beneath skin (angioedema), and severe allergic reactions (anaphylactic shock).

What Causes Atopy?

The cause of atopy, or a tendency toward allergies, is not well-understood. However, studies involving twins, families, and animals, along with epidemiological research, suggest that genes play a big role. Specifically, certain genes can cause the body to produce too much IgE, a type of protein that’s involved in allergic reactions. While it’s clear that allergies can run in families, the exact pattern of inheritance appears to involve multiple genes.

One theory behind atopy involves T-helper cells and suppressor T lymphocytes, two types of immune cells. These cells may help plasma cells (another type of immune cell) to make IgE. Certain genes associated with atopy include those found on chromosome 5q and those involving cytokines (proteins that play a role in immune responses), CD14, a growth-stimulating factor called GM-CSF, and β2-adrenergic receptors.

IL-4 and IL-13 promote the switch to IgE, while IL-5 stimulates the growth and activation of eosinophils, another type of immune cell. Chromosome 6p contains genes for a protein complex called MHC class II, some of which help T-cells respond to environmental antigens or allergens. Meanwhile, a gene on chromosome 11q makes the beta-subunit of the high-affinity IgE receptor, which is involved in mast cell activation. Chromosome 12q holds genes that create proteins affecting mast cell growth and differentiation, as well as immune regulation and signaling.

Additional genes tied to atopy code for proteins involved in immune regulation and responses, airway remodeling and B cell and immunoglobulin expression. Pathways outside of genetics, such as infections, environmental factors, physical activity, and certain medications can also trigger asthma, a condition often associated with atopy.

Finally, numerous substances in the workplace can trigger allergic asthma, a condition in which the body’s immune response to allergens causes breathing difficulties. These include animal products, insect dust, plant products, gums and extracts, microbial agents, enzymes, therapeutic agents, sterilizing agents, as well as both inorganic and organic chemicals.

Risk Factors and Frequency for Atopy

Atopy, a type of allergy, affects a significant part of the population in developed countries – between 10% and 30%. About 80% of people with atopy have a family history of allergies, implying a genetic factor. However, it’s not just one or two major genes at play; multiple genes interact to cause atopy. Also interesting is that identical twins only share atopy 50% of the time.

Allergic rhinitis, or hay fever, affects 10% to 12% of people in America. The spread and seriousness of this condition vary across the country based on local allergens, with dust mites and allergy-causing plants being the most common. This condition affects males and females equally.

• Bronchial asthma is another condition whose prevalence varies globally. It affects about 5% of people in Western countries.
• This condition causes over 3,000 deaths each year in the US, and the number of cases and the severity of those cases are increasing despite advancements in immunotherapy.
• As of 2014, 8.4 million children in the US were living with asthma, with 11.1% of these children living in low-income, urban areas.

Signs and Symptoms of Atopy

Atopic diseases are related to a person’s overly sensitive immune response to common allergens and they usually have high levels of a certain type of antibody, IgE, in their blood. People with these conditions normally won’t have symptoms unless they come into contact with the allergens that trigger their immune response. The conditions discussed here are atopic rhinitis, allergic asthma, atopic dermatitis, and food allergies. Each of these have their own particular symptoms and factors:

Atopic Rhinitis:

• Stuffy nose
• Runny nose
• Sneezing
• Itchy nose
• Post-nasal drip (mucus dripping down the back of the throat)
• Dry cough
• Eye symptoms
• Nasal examination showing a pale, swollen inner nose with watery secretions
• Red and swollen inner surface of the eyelids

Allergic Asthma:

• Can start at any age
• Frequent episodes of wheezing and shortness of breath
• Feeling of tightness in the chest
• Coughing (especially at night in children), often with sticky and tenacious sputum
• Fatigue
• Feeling unwell
• Overuse of muscles not normally used for breathing
• Lungs may produce unusually resonant sounds
• Breath sounds may be faint
• Breathing sounds may be whistling or rattling
• Prolonged breathing out phase

Atopic Dermatitis:

• Usually starts in infancy
• Itching is more noticeable at night and worsened by irritants such as wool
• Often there’s a strong family history of atopy
• Scratching and rubbing can cause the typical itchy, inflamed skin rash
• Flare-ups may happen after eating food that causes an allergic reaction
• Dry and flaky skin
• Active skin lesions can be itchy and red
• Chronic lesions can become thick and hardened
• The distribution of lesions can change with age and during childhood, the forehead and cheeks are commonly affected

Food Allergies:

• Causes symptoms similar to rhinitis and conjunctivitis
• Can trigger asthma
• Can cause low blood pressure
• Can lead to abnormal heart rhythms
• Can cause nausea and vomiting
• Abdominal cramping
• Diarrhea
• Often causes anaphylaxis, a severe allergic reaction affecting the entire body
• It’s rare for respiratory symptoms to be the only ones present

Testing for Atopy

If your doctor suspects that you’re suffering from immediate hypersensitivity, which is like a fast allergic reaction, they will perform a host of tests. The first tests they’d conduct include a blood test, a test for a protein called IgE, and a skin prick test.

In addition to the aforementioned tests, the doctor may recommend:

1. Tests to check Immunoglobulins – These are proteins in your blood and include IgM, IgG, and IgA.

2. Total White Blood Cell Count – This test will give details about your hemoglobin levels, which might be low if you have a condition called autoimmune hemolytic anemia. It will also test for eosinophilia or an excess of a specific type of white blood cell and run tests on lymphocytes like CD4/CD8 count and suppressor T-cell count. These could be lower than normal.

3. Allergy Tests – These involve a skin prick test with various allergens like animal dander, plant pollen, food substances, harmful microbes, and pollutants. The doctor also may order a radioallergosorbent test (RAST) to identify specific IgE antibodies in your blood.

4. Other Tests – Some other necessary tests might include Serum protein electrophoresis to rule out a condition called IgE myeloma. A stool exam might be requested to check for intestinal parasites. Depending on the situation, the doctor might suggest a specific diet and provocation tests to help diagnose food allergies more clearly. Lastly, a chest x-ray might be needed to check for bronchial asthma.

Treatment Options for Atopy

Allergic rhinitis, often known as hay fever, is treated by controlling exposure to allergens, taking medication, and in some cases, using a process called desensitization. It’s best to avoid allergens but if you can’t, medication can help control symptoms. Taking certain steps can keep allergens out of your environment. This includes things like not having pets in the house, dusting frequently to reduce the amount of house dust, and avoiding toys that accumulate dust. Some small devices can help clean air and reduce allergen presence. You can also prevent dust and mold from building up outdoors. Antihistamines are commonly used and newer ones have fewer side effects. Nasal decongestants can be used along with antihistamines for relief. Specially treated eye-drops can help if you have an allergic eye reaction. A spray called nasal cromolyn, used four times a day, can help and has no immediate or long-term toxicity. Systemic corticosteroids can reduce symptoms but should only be used briefly.

Allergic Asthma is similar to allergic rhinitis but affects the bronchus, a part of the lung. Treatments include controlling the environment, medication, and other therapies. Bronchodilators are used for immediate relief of an attack and long-term management. They are usually inhalers. Other medications such as theophylline, epinephrine are used during an acute asthma attack. Glucocorticoids are beneficial but should be used only for asthma that is not responding to other treatments. You can use inhalers for long-term preventative treatment, but they won’t be helpful in an acute attack. Antibiotics might be used if there’s a secondary bacterial infection in the bronchi. Desensitization is also useful in cases of allergic asthma.

Atopic dermatitis, or eczema, is a skin condition treated by taking care of the skin, controlling the environment, medication, and avoiding allergens. Lubricating the skin can prevent itching. For mild cases, steroid creams can help. For more severe cases, steroid tablets may be needed. Itching can also be controlled with antihistamines. Avoid frequency bathing and irritating fabrics. Antibiotics may be needed if an infection sets in.

Food allergies are treated by strictly avoiding the food that causes allergic reactions. It’s crucial to have an emergency plan in case of accidental ingestion. Self-injectable epinephrine should be always with the patient. The most common food allergens in children are cow’s milk, soy, wheat, eggs, and peanuts. For adults, the primary culprits are fish, shellfish, peanuts, tree nuts, eggs, fruits, and vegetables.

Immunotherapy for allergies, such as allergic rhinitis, asthma, and atopic dermatitis has improved significantly. Research in Monoclonal antibodies and cytokines are promising. Monoclonal antibodies are protein molecules that help in fighting diseases causing factors. They target specific proteins or cells involved in allergic reactions. Cytokines are small proteins secreted by immune system cells. There are several being researched in the treatment of allergies.

Allergy immunotherapy, also called desensitization or allergy shots, involves giving increasing doses of allergens to reduce the allergic response. This therapy can be given via injections into the skin, or tablets or drops under the tongue. Monoclonal antibodies and cytokines research is offering new possibilities for personalized therapies. Allergy immunotherapy continues to be a critical part of long-term management, especially when allergen avoidance or conventional medications aren’t enough.

What else can Atopy be?

When a person has high levels of IgE (a type of antibody) in their blood, a doctor might consider the following potential causes:

• Allergic bronchopulmonary aspergillosis
• Parasitic diseases
• Immunodeficiency with ataxia-telangiectasia (a rare condition that affects the nervous system and immune system)
• Hyper-IgE syndrome (an immune system disorder)
• Wiskott-Aldrich syndrome (a rare condition that affects the immune system and blood cells)
• IgE myeloma (a type of cancer that starts in the plasma cells)
• Thymic alymphoplasia (a condition that causes lack of certain white blood cells)
• Graft-versus-host reaction (an immune response seen after certain types of transplants)

If a patient is experiencing symptoms similar to those of atopic rhinitis (hay fever), a doctor might also consider these possible causes:

• Chronic nonallergic rhinitis
• Rhinitis medicamentosa (caused by overuse of nasal decongestants)
• Infectious rhinitis (a nose infection)
• Vernal keratoconjunctivitis (a form of eye inflammation)

If a patient has symptoms that resemble allergic bronchial asthma, the physician may consider the following alternatives:

• Pulmonary emphysema (damage to the lungs)
• Acute bronchiolitis (inflammation of the small airways in the lungs)
• Cystic fibrosis (a genetic disorder that damages the lungs and digestive system)
• Foreign body aspiration (accidentally inhaling an object)
• Airway obstruction caused by a birth defect in blood vessels
• Cardiac asthma due to heart failure
• Carcinoid tumors (rare, slow-growing tumors that can occur in several places in your body)

Finally, if a patient has symptoms similar to those of atopic dermatitis (eczema), the doctor might also consider these possible causes:

• Localized neurodermatitis (an itch-scratch cycle)
• Allergic or irritant contact dermatitis (skin reaction caused by contact with a certain substance)
• Seborrhea and dermatophytoses (common skin conditions)
• Pompholyx (a type of eczema that causes tiny blisters on hands or feet)

What to expect with Atopy

People with atopy are usually prone to allergic reactions all their life because there’s no cure for this condition. However, how it shows up can change over time. Atopic dermatitis, a type of skin condition, tends to improve with time and treatments aimed at boosting the immune system can help manage its symptoms. The outlook for allergic asthma can differ depending on various things like how long the allergen, or substance causing the allergy, stays around, how much of a certain antibody called IgE exists in the blood or tissues, and the patient’s genetic makeup.

Anaphylaxis, which can affect different parts of the body at the same time, is caused by a strong reaction to an allergen. This can be triggered by anything from insect venom to food or medication. It can be life-threatening, and even a tiny bit of the allergen can set it off. Quick medical help is essential as the outlook for patients with anaphylaxis can often be quite serious.

Possible Complications When Diagnosed with Atopy

Allergic Rhinitis, Allergic Bronchial Asthma, Atopic Dermatitis, and Anaphylaxis all present different complications. Here’s a simple list of these complications:

The complications of Allergic Rhinitis include:

• Sinusitis
• Otitis media
• Nasal polyps
• Apnea

Complications from Allergic Bronchial Asthma:

• Pneumothorax
• Subcutaneous emphysema

Complications of Atopic Dermatitis:

• Infections caused by Staphylococcus germs
• Eczema herpeticum
• Dermatitis caused by contact with antibiotics
• Dermatitis on hands from too much washing
• Eye complications, including keratoconjunctivitis, keratoconus, and cataracts related to atopic conditions

Anaphylaxis is an emergency situation that can threaten the life of an individual, leading to acute respiratory failure. Specifics about Anaphylaxis include:

• It is caused by an IgE-mediated reaction, which is a rapid release of histamines and leukotrienes from mast cells.
• Severe instances can cause swelling in the larynx (voice box), bronchial spasms, low blood pressure, blueness of skin (cyanosis), and shock.
• Certain drugs and additives are known to cause reactions similar to anaphylaxis, such as NSAIDs (like aspirin, aminopyrine, and others), opioids (like morphine, codeine, and others), mannitol, certain dyes used for scans, dextran, curare, and d-tubocurarine.
• Reactions that are similar to anaphylaxis should be treated in the same way.

Preventing Atopy

Teaching patients and their families about their condition is truly essential. For children’s health in particular, this means giving parents important information, especially about how to recognize and eliminate whatever might be causing a problem. It’s also important to teach patients how to deal with these issues when they first arise, and when it’s necessary to get help from a healthcare professional.