Allergies – Causes, Symptoms, Treatments

What are Allergies ?

Allergies are an overreaction by your body’s immune system to a typically harmless substance called an allergen. These allergens can be things like pollen, dust mites, pet dander, or certain foods.

Prevalence of Allergies

Estimates suggest that allergies affect a significant portion of the population worldwide. In the United States alone, studies indicate that over 50 million people have allergies. Allergies can develop at any age, from infancy to adulthood. However, they are most commonly diagnosed in childhood.

The majority of allergies, particularly food allergies and some respiratory allergies like allergic rhinitis (hay fever), are first diagnosed in childhood.

While some allergies, particularly food allergies to milk, eggs, wheat, or soy, may be outgrown in childhood, others like peanut and tree nut allergies tend to be lifelong.

It’s important to note that allergies can develop for the first time in adults as well. While less common than childhood allergies, adult-onset allergies can occur at any point from young adulthood onwards. The reasons for this are not fully understood, but factors like increased exposure to certain allergens or changes in the immune system may play a role.

How do Allergies Develop?

Allergies stem from the body’s immune system overreacting to a harmless substance, mistakenly identifying it as a threat. Here’s a deeper look at the development process:

The Allergic Response:

• Normal Immune Response: The immune system is designed to protect the body from invaders like bacteria, viruses, and parasites. When it encounters a foreign substance, it triggers an immune response to neutralize and eliminate the threat.
• The Misguided Response in Allergies: In allergies, the immune system mistakenly identifies a harmless substance, like pollen or dust mites, as a dangerous invader. This triggers an inappropriate immune response, leading to the production of antibodies (IgE) specific to that allergen.
• Sensitization: The first exposure to an allergen can initiate this process, sensitizing the immune system. During this initial exposure, the body produces IgE antibodies specific to the allergen. These antibodies attach to immune cells called mast cells, which circulate throughout the body.
• The Reaction Upon Re-exposure: Upon subsequent exposures to the same allergen, the allergen binds to the IgE antibodies already attached to mast cells. This triggers the mast cells to release a cascade of inflammatory chemicals, including histamine.

Histamine and its effects:

• Histamine’s Role: Histamine is a key mediator of allergic symptoms. It acts on various tissues in the body, causing the characteristic signs and symptoms of allergies, such as:
  • Dilation of blood vessels leading to redness, itching, and swelling
  • Increased mucus production leading to a runny nose or congestion
  • Contraction of smooth muscles in the airways leading to wheezing and difficulty breathing

Individual Predisposition:

• Genetics: A genetic predisposition plays a role in allergies. If you have a family history of allergies, you’re more likely to develop them yourself. Genes can influence how your immune system reacts to allergens.
• Hygiene Hypothesis: The hygiene hypothesis suggests that early childhood exposure to a wider variety of microbes might help train the immune system and reduce the risk of allergies. However, the research on this is ongoing and not fully conclusive.

The severity of the allergic reaction depends on the amount of histamine released and the individual’s sensitivity. In severe cases, allergies can lead to anaphylaxis, a life-threatening reaction that requires immediate medical attention.

What are the Levels of Severity of Allergic Reactions?

Allergic reactions can be a surprising experience, ranging from a minor inconvenience to a life-threatening emergency. The severity of the reaction and the bodily systems affected can vary greatly from person to person, even with exposure to the same allergen.

The severity of an allergic reaction depends on several factors, including the type and amount of allergen exposure, an individual’s sensitivity, and the specific body systems involved. Mild reactions might cause sneezing, itchy eyes, or a rash, while moderate reactions can involve wheezing, coughing, or hives. Severe allergic reactions, known as anaphylaxis, are potentially life-threatening and require immediate medical attention. 

Symptoms of anaphylaxis can include a combination of skin reactions (hives, itching, swelling), respiratory problems (wheezing, trouble breathing), cardiovascular issues (rapid heartbeat, weak pulse), and digestive problems (abdominal cramps, nausea, vomiting). In severe cases, a person experiencing anaphylaxis may also feel faint or lightheaded.

Seasonal Allergies

Seasonal allergies, often referred to as hay fever or allergic rhinitis, are triggered by airborne allergens that fluctuate throughout the year. Unlike allergies to dust mites or pet dander, which can occur year-round, seasonal allergies follow a predictable pattern based on the prevalence of the allergens in the environment. 

• Trigger by Airborne Allergens: The hallmark feature of seasonal allergies is their sensitivity to airborne allergens, most commonly pollen from wind-pollinated plants like trees, grasses, and weeds.
• Symptoms: When exposed to these allergens, the immune system overreacts, causing a cascade of inflammatory responses. This leads to the characteristic symptoms of hay fever, including:
  • Sneezing
  • Runny or stuffy nose
  • Itchy, watery eyes
  • Itchy sinus passages or throat
  • Postnasal drip (drainage down the back of the throat)
  • In some cases, fatigue, headaches, and even facial pressure or pain can occur.

Seasonal Fluctuations:

• Pollen Counts: The severity of seasonal allergies is closely linked to pollen counts in the air. Tree pollen tends to be most prevalent in early spring, while grass pollen plagues sufferers in late spring and summer. Fall brings on ragweed season, another notorious trigger for seasonal allergies. Knowing the pollen types and their peak seasons in your area can help you anticipate and manage your symptoms.
• Location Dependence: The specific timing and types of allergens can vary depending on your location. For instance, regions with long winters might experience a shorter allergy season compared to places with milder climates. Understanding the common allergens in your area and their peak seasons is key to effective management.

Individual Variations:

• Multiple Sensitivities: It’s important to note that some people can be sensitive to multiple airborne allergens, experiencing allergy symptoms for extended periods throughout the year as different pollens become dominant.
• Non-Allergic Rhinitis: Not all cases of a runny or stuffy nose during seasonal changes are due to allergies. Other factors like irritants in the environment (dust, smoke) or even changes in temperature and humidity can trigger similar symptoms. Consulting a healthcare professional can help distinguish between seasonal allergies and other causes.

Food Allergies

A food allergy occurs when the body’s immune system mistakenly identifies a particular food protein as a harmful invader. This triggers an inappropriate immune response, leading to a cascade of symptoms that can range from mild discomfort to a life-threatening reaction known as anaphylaxis. 

A healthy immune system plays a vital role in protecting the body from germs like bacteria, viruses, and parasites. When it encounters a foreign substance, it launches an immune response to neutralize and eliminate the threat.

In food allergies, the immune system mistakenly identifies a specific protein in a food, often harmless, as a dangerous invader. This triggers the production of specific antibodies (IgE) designed to fight this perceived threat.

The first time someone encounters the food protein, their immune system may become sensitized. This means the body produces IgE antibodies specific to that particular protein. These antibodies attach to immune cells called mast cells, which are located throughout the body, essentially priming them to react if they encounter the allergen again.

Upon subsequent exposures to the same food, the food protein binds to the IgE antibodies already attached to mast cells. This triggers the mast cells to release a flood of inflammatory chemicals, including histamine.Histamine is a key mediator of allergic symptoms. 

It acts on various tissues in the body, causing the characteristic signs and symptoms of food allergies, such as:

• Skin reactions: Hives, itching, eczema, swelling
• Digestive problems: Nausea, vomiting, diarrhea, abdominal cramps
• Respiratory issues: Wheezing, coughing, trouble breathing (in severe cases)
• In rare cases, a severe allergic reaction (anaphylaxis) can occur, affecting multiple body systems and requiring immediate medical attention.

Common Food Allergens:

While food allergies can develop to practically any food, some proteins are more frequent culprits than others. Here are some of the most common food allergens:

• Peanuts: Peanut allergies are one of the most common food allergies, and they can be very severe. Even small amounts of peanut exposure can cause a serious reaction.
• Tree Nuts: Other tree nuts, such as almonds, walnuts, cashews, pecans, and pistachios, can also trigger allergic reactions. People with peanut allergies may also be allergic to tree nuts, but this is not always the case.
• Milk: Milk allergy is a common childhood food allergy, but some adults may also have it. Milk allergy is a reaction to the proteins in cow’s milk.
• Eggs: Eggs are another common food allergen, particularly the protein in egg whites.
• Soy: Soy allergy is becoming increasingly common, and it can cause reactions ranging from mild to severe. Soy is found in many processed foods, so careful reading of food labels is crucial for people with soy allergies.
• Wheat: Wheat allergy is a reaction to the gluten protein found in wheat. People with wheat allergy typically experience digestive problems after consuming wheat products. However, a separate condition, celiac disease, also involves gluten but has a different immune system mechanism.
• Shellfish: Shellfish, such as shrimp, crab, lobster, and clams, are a common food allergen. Shellfish allergies tend to be lifelong, and reactions can be severe.
• Fish: Fish allergy is less common than shellfish allergy, but it can still cause serious reactions. People with fish allergies may need to avoid all types of fish or only specific types, depending on the severity of their allergy.

Skin Allergies

Skin allergies can be caused by two main mechanisms: an immune system reaction (hypersensitivity) or direct irritation from a substance. Hives, also known as urticaria, are raised, itchy welts that appear on the skin’s surface. They can be red, pink, or skin-colored and vary in size and shape. Hives can appear suddenly and spread rapidly, affecting any part of the body. The primary symptom associated with hives is intense itching, which can be quite bothersome. In some cases, there may also be a burning or stinging sensation.

Angioedema is a deeper swelling that occurs in the lower layers of the skin. It typically affects the face, lips, eyelids, or genitals, causing puffiness and a feeling of tightness. Unlike hives, angioedema is not usually itchy. The main symptom of angioedema is swelling, which can be localized or widespread. In severe cases, angioedema affecting the airway can cause difficulty breathing, a medical emergency requiring immediate attention.

Hypersensitivity Reactions:

• Allergic contact dermatitis: This is a common type of skin allergy caused by a direct touch reaction to an allergen. The allergen triggers an immune system response in the skin, leading to inflammation. Symptoms typically appear within 12-48 hours of exposure and usually develop at the site of contact. Common allergens include poison ivy, nickel (found in jewelry), latex, and certain skincare products. Symptoms can include redness, itching, blistering, and even crusting or oozing of the affected area.
  
  
• Atopic dermatitis (eczema): While eczema can have non-allergic triggers as well, it can also be worsened by allergies. In this case, exposure to allergens like dust mites, pet dander, or pollen can trigger flare-ups of eczema, leading to intensely itchy, dry, and inflamed patches of skin. Eczema can affect any part of the body but commonly appears on the hands, face, inner elbows, and knees in adults and infants.

Other less common hypersensitivity reactions affecting the skin include:

• Papular urticaria: This condition causes small, itchy bumps surrounded by a red halo, often triggered by insect bites or medications.
• Serum sickness: This is a rare allergic reaction to medications or foreign proteins, causing symptoms like fever, rash, and joint pain.

Irritant Contact Dermatitis:

• This is a non-allergic inflammatory skin reaction caused by direct contact with an irritating substance. Unlike allergic contact dermatitis, irritant contact dermatitis does not involve the immune system. Anyone can develop irritant contact dermatitis with enough exposure to the irritant. Common irritants include soaps, detergents, solvents, harsh chemicals, and friction. Symptoms typically appear soon after contact and can include redness, itching, burning, and dryness. In severe cases, blistering may occur.

Allergic Asthma

Allergic asthma is the most common form of asthma, affecting a significant portion of both children and adults with the condition. In allergic asthma, a person’s airways become inflamed in response to the presence of allergens, substances that trigger an immune system response. This inflammation narrows the airways, making it difficult to breathe and leading to characteristic symptoms like wheezing, coughing, chest tightness, and shortness of breath.

Common allergens that can trigger these symptoms in people with allergic asthma include inhaled allergens such as pollen from trees, grasses, and weeds. The severity of these triggers can vary depending on the season and location. Dust mites, microscopic organisms found in dust, are another frequent culprit. They thrive in warm, humid environments, and people with allergic asthma may find their symptoms worsen in such conditions. 

Mold spores, tiny airborne particles released by mold that grows in damp areas, can also induce asthma attacks. Additionally, animal dander, tiny flakes of skin shed by animals with fur or feathers, is a common trigger for allergic asthma. In some cases, even cockroach waste particles can be problematic for people with allergies, even if they don’t see the insects themselves. Certain workplace environments can also pose a risk, with dusts, chemicals, or fumes triggering asthma symptoms in susceptible individuals.

It’s important to remember that the specific allergens that trigger asthma can vary greatly from person to person. Someone with allergic asthma might experience a severe reaction to pollen, while another might be more sensitive to dust mites. Even in people with allergic asthma, exposure to other irritants, such as smoke or cold air, can worsen their asthma symptoms.

Prevention Measures

Living with allergies doesn’t have to mean constant struggle. By incorporating preventive measures into your daily routine, you can significantly reduce your risk of exposure to allergens and lessen the severity of symptoms when exposure does occur. Get a diagnosis from a doctor or allergist to pinpoint your specific allergens. Once you know what substances trigger your allergies, you can develop a personalized plan to avoid them.

• For seasonal allergies to pollen, stay informed about pollen counts in your area. Limit outdoor activities or wear a pollen mask during high pollen times. Close windows during peak pollen times and shower after spending time outdoors.
• Minimize dust mites by encasing mattresses and pillows in allergen-proof covers, washing bedding frequently in hot water, and vacuuming carpets and furniture regularly. Consider using a HEPA filter vacuum cleaner.
• Address moisture problems in your home to prevent mold growth. Regularly clean and dry bathrooms and kitchens, and promptly fix leaks.
• If allergic to pet dander, avoid close contact with pets, bathe them regularly, and keep them off furniture and out of the bedroom. HEPA air filters can also help capture pet dander particles.

Maintain Clean Surroundings

• Air Purification: Consider using air purifiers with HEPA filters in your home, particularly in the bedroom. These can help remove allergens from the air you breathe.
• Regular Cleaning: Maintain a clean indoor environment by vacuuming carpets and furniture regularly, dusting frequently with a damp cloth, and washing floors with appropriate cleaning solutions.

Food Allergy Attentiveness:

• Label Literacy: For individuals with food allergies, carefully scrutinize food labels, paying close attention to ingredients and allergen warnings. When in doubt, avoid the food altogether.
• Clear Communication: Inform restaurants or hosts about your food allergies beforehand. Discuss menu options and potential modifications to ensure your meal is safe for consumption.

Diagnosing Allergies

Diagnosing allergies often involves a two-pronged approach: a detailed medical history and allergy testing. Here’s a breakdown of the process:

Medical History:

• Doctor Consultation: The first step usually involves a consultation with a doctor or allergist (a specialist in allergies and immune system conditions). During this visit, the doctor will gather a comprehensive medical history, including:
  • Symptoms: A detailed description of your symptoms, including their frequency, severity, and any potential triggers you’ve noticed.
  • Personal and Family History: Information about your personal history of allergies and any allergies present in your family members. This can provide clues about your susceptibility.
  • Lifestyle and Environmental Factors: Exploring your lifestyle and environment to identify potential allergen exposures, such as pets, dust mites, pollen counts in your area, or occupational hazards.

Allergy Testing:

Once the doctor has a better understanding of your symptoms and background, they may recommend allergy testing to pinpoint the specific allergens causing your reactions. Here are two common methods used for allergy testing:

• Skin Prick Test: This is the most common and often the first-line test used for allergy diagnosis. It’s a relatively quick and minimally invasive procedure. During the test, a small amount of a suspected allergen (in liquid form) is pricked onto the skin’s surface, usually on the forearm or back. The healthcare provider then observes the area for a reaction, typically a raised, itchy bump (wheal) within 15-20 minutes. The size and presence of these wheals indicate the body’s sensitivity to the tested allergens.
• Blood Test (Specific IgE): A blood test, also known as a specific IgE (immunoglobulin E) test, can be an alternative if skin testing is not suitable. This might be the case if you have extensive skin conditions that interfere with skin prick testing or if you’re taking certain medications that can affect skin test results. A blood test measures the amount of specific IgE antibodies produced by your immune system in response to various allergens. While convenient, blood tests may not always be as sensitive as skin prick tests for detecting certain allergies.

Additional Tests:

In some cases, additional tests like a nasal challenge test or a bronchial challenge test may be used for specific situations. These involve controlled exposure to suspected allergens, typically under medical supervision, to confirm a diagnosis. However, these tests are not as commonly used as skin prick tests or blood tests.

How are Allergies Treated?

Allergies can significantly impact a person’s quality of life. Fortunately, with proper diagnosis and a tailored treatment plan, allergy symptoms can be effectively managed. The most successful approach considers several factors to create a personalized strategy for you.

Firstly, there’s no one-size-fits-all solution. Your individual needs and circumstances are key. The type and severity of your allergies, your age, overall health, and lifestyle all influence the best course of action. For instance, a child with mild seasonal allergies might benefit from a different treatment plan than an adult with severe dust mite allergies.

Once you and your doctor have a clear understanding of your allergies, you can explore various treatment options, which are often used in combination for optimal control. The cornerstone of allergy management is allergen avoidance whenever possible. This involves identifying your triggers through testing and then taking steps to minimize exposure. If dust mites are your culprit, using allergen-proof mattress covers and washing bedding regularly can significantly reduce symptoms.

Medications can also play a vital role in managing allergy symptoms. The specific medication will depend on the type and severity of your allergies. Antihistamines are a common choice, blocking the action of histamine, a chemical released by the immune system during an allergic reaction, and can help alleviate symptoms like sneezing, itching, runny nose, and watery eyes. Corticosteroids, particularly nasal corticosteroids, can reduce inflammation in the nasal passages, relieving congestion and stuffiness associated with allergies. Decongestants can also be helpful, but consult your doctor before using them for extended periods.

In some cases, a more long-term approach might be recommended. Allergen immunotherapy, also known as allergy shots or sublingual tablets, aims to gradually desensitize your immune system to the allergens that trigger your reactions. This approach doesn’t offer a quick fix, but with consistent use over time, your immune system can become less reactive to the allergen, leading to a significant reduction in allergy symptoms.

Other therapies, like nasal saline irrigation or allergy eye drops, may also be recommended to help soothe and cleanse irritated tissues.

What Medications are Most Prescribed for Allergies?

Here are some of the most commonly prescribed medications for allergies, categorized by their function:

• Antihistamines: These medications block the action of histamine, a chemical released by the immune system during an allergic reaction. Histamine causes many allergy symptoms, so antihistamines can be helpful in relieving a variety of them.

Some examples of commonly prescribed antihistamines include:

• Loratadine (Claritin)
• Cetirizine (Zyrtec)
• Fexofenadine (Allegra)
• Diphenhydramine (Benadryl)  

Corticosteroids: These medications reduce inflammation, which can be helpful for allergies that cause swelling and congestion. Corticosteroids are available in several forms for allergy treatment:

• Nasal corticosteroids: Sprayed directly into the nose to target allergy symptoms like congestion, rhinitis (inflammation of the nasal passages), and postnasal drip (drainage down the back of the throat). Examples include budesonide (Rhinocort), fluticasone (Flonase), and mometasone (Elocon).
• Oral corticosteroids: Typically prescribed for short-term use in severe allergic reactions. Due to potential side effects, these are not a first-line treatment for most allergies.

Decongestants: These medications help shrink swollen nasal tissues, easing congestion and stuffiness. However, decongestants should not be used for extended periods without consulting a doctor, as overuse can lead to a condition called rhinitis medicamentosa (medication-induced rebound congestion).

Some examples of commonly used decongestants include:

• Pseudoephedrine (Sudafed)
• Phenylephrine (Sudafed PE)
• Oxymetazoline (Afrin)

Leukotriene Modifiers: These medications block the action of leukotrienes, another group of chemicals involved in the inflammatory response during allergic reactions. Leukotriene modifiers are typically used for allergies that cause asthma symptoms, such as wheezing and difficulty breathing.

An example of a commonly prescribed leukotriene modifier is montelukast (Singulair).

Allergy immunotherapy (allergy shots or sublingual tablets): This is not technically a medication but a treatment approach that aims to gradually desensitize your immune system to the allergens that trigger your reactions. Over time, with consistent use, allergy immunotherapy can lead to a significant reduction in allergy symptoms.