SCIENCE30 - Understanding Allergies

Once again, Pat came up with this topic for a blog.  Thank you.  Thank you.  As an extra incentive for me, I suffer from allergies, including an allergy to penicillin and dust, so I wanted to know more about allergies.

 

After a short introduction, I will discuss the history of our knowledge of allergies, and then types of allergies and reactions, more on food allergies, diagnosis of allergies, and management and treatment of allergies.  I will conclude with some interesting facts about allergies.

As usual, I will list my principal sources at the end.

 

Introduction

Allergies are overreactions by your immune system to usually harmless substances called allergens that can be airborne, touch your skin, are present in some foods, and in some medications (see below).

When you inhale, touch, or eat something (or get stung by a bee) that you’re allergic to, your body thinks it’s harmful and reacts by trying to get rid of it by making protective proteins called antibodies that attack invaders such as germs.  But with allergies, the immune system makes antibodies that mark a specific allergen as harmful, even though it normally isn't.  This can cause minor reactions like itching, sniffling, and sneezing, but in some cases, allergic reactions can lead to life-threatening airway swelling and low blood pressure (anaphylaxis).

Hay fever (allergic rhinitis) and asthma are special cases of allergies. 

Allergic reactions vary from person to person.  Some people have allergies that are merely annoying.  Others must completely alter their lives to avoid reactions.

 

History of our Knowledge of Allergies

Knowledge of allergies evolved from ancient anecdotal accounts of "poisonous" reactions to a sophisticated modern understanding of the immune system's overreaction to normally harmless substances.  Here is a timeline of important events:

 

2700 BC - AD 1500: Early Records and Anecdotes.

c. 2700 BC: Early records described mysterious adverse reactions to some foods.  

c. 2600 BC: Egyptian Pharaoh Menes is believed to have died from anaphylactic shock following a wasp sting.  Asthma was recognized in ancient Egypt and was treated by drinking an incense mixture known as kyphi. 

c. 450 BC: Asthma was officially named as a specific respiratory problem by Hippocrates c. 450 BC, with the Greek word for "panting" forming the basis of our modern name.  Hippocrates also noted strange reactions to cheese.

First century BC: Roman poet and philosopher Lucretius famously noted that "what is food for some may be fierce poison for others.”  

1483: King Richard III of England reportedly suffered an immediate rash after eating strawberries, which he attributed to a rival's curse.  Also in the Medieval Period, Persian-Arabic literature called hay fever "rose fever," and the Talmud discussed remedies for asthma. 

 

19^th - Early 20^th Century: Scientific Beginnings.

1819:  English physician and scientist Dr. John Bostock provided the first clinical description of seasonal (summer) hay fever, which he suffered from personally.

1873: English medical doctor Charles Blackley proved pollen caused hay fever by experimenting on himself with grass pollens.

1902: French scientists Charles Richet and Paul Portier coined the term "anaphylaxis" after studying severe allergic reactions.  The word “anaphylaxis” comes from Greek, combining "ana-" (against, without) and "phylaxis" (protection), meaning "against protection" or "lack of protection.” 

1906: The term "allergy" was created by Austrian scientist and pediatrician Clemens von Pirquet.  Derived from the Greek words allos ("other") and ergon ("work"), he used it to describe an altered immune state where a substance triggers a harmful rather than protective response.

Austrian scientist and pediatrician Clemens von Pirquet coined the word “allergy.”

Early 20^th Century: Diagnosis and Early Treatment.

1900s-1910s: Early immunotherapy (allergy shots) developed by Englishmen Noon & Freeman.

1912: American physician Oscar Schloss demonstrated a food allergy (egg) diagnosis via skin scratch tests.

1930s: Antihistamines developed; clinically available in the 1940s to block histamine, a chemical your body releases during allergic reactions, treating symptoms like sneezing, itching, and runny nose.

1948: Corticosteroids were first used for allergies by American doctors Philip Hench and Edward Kendall, revolutionizing treatment by targeting inflammation, a key component of allergic responses.

 

Mid-to-Late 20^th Century: Unlocking Mechanisms & Better Treatments.

1950s: “Mast” cells identified as the immune system's first responders, triggering inflammation, fighting pathogens (bacteria, viruses, fungi), regulating other immune cells, and mediating allergic reactions by rapidly releasing potent chemicals like histamine and cytokines (proteins acting as messengers for cell-to-cell communication). 

1967: Discovery of Immunoglobulin E (IgE) antibody by two independent teams, headed by Japanese immunologist Kimishige Ishizaka and Swedish psychophysicist Gunnar Johansson.  This antibody was identified as the primary antibody responsible for most allergic reactions. 

Japanese immunologist Kimishige Ishizaka headed the American team that discovered the primary antibody responsible for most allergic reactions.

1970s: Discovery of leukotrienes, important contributors to inflammation in asthma/allergies.

1970s-1980s: Corticosteroid nasal sprays gain prominence; second-generation antihistamines (less drowsy) developed. 

 

Late 20^th Century and Early 21^st Century: Epidemics & Modern Therapies.

1980s-90s. Rise of pediatric asthma linked to indoor lifestyles.

1990s. Dramatic increase in food allergies.

2000s-Present: Development of leukotriene (inflammation) blockers, refined immunotherapy (more convenient, and faster ways to build tolerance to allergens), and multi-symptom nasal sprays; focus on introducing early food allergens to babies to build up tolerance and prevent allergies. 

Food allergies are now considered an "epidemic" due to their rapid, significant rise globally, especially in Western countries, affecting millions with increased severity, leading to more hospitalizations, and prompting research into environmental triggers like changes in gut microorganisms, vitamin D, hygiene, and lifestyle factors. The numbers are stark:  Over 32 million Americans have food allergies, with a notable increase in both children and adults, including many developing allergies as adults. 

By 2025, an estimated 30% to 40% of the global population lives with some form of allergy, a number that continues to increase due to environmental changes and urban lifestyles.

Types of Allergies and Reactions

Generally, common allergens are airborne, touch the skin, are present in food, or are present in medications.  The following figure identifies some of the common allergens.

Airborne. Seasonal allergens like tree, grass, and ragweed pollen cause sneezing runny nose, and itchy eyes.  Year-round indoor dust mites in bedding and mold in damp areas, cause congestion and sneezing.  Many people are allergic to pet dander, saliva, or urine - common with cats, dogs, and other furry animals.

Note: Animals can have allergies too, just like humans, with common triggers including fleas, food ingredients (like dairy, wheat, corn), and environmental factors (pollen, dust, mold), leading to symptoms like intense itching, skin irritation, ear infections, or digestive issues.  While more common in pets, allergies can affect various species, from dogs and cats to horses and even zoo animals, often appearing as skin problems. 

Hay fever (allergic rhinitis) is an immune system response to airborne allergens, causing symptoms like sneezing, runny nose, and itchy eyes, and while it's seasonal, it can sometimes last for months.  With allergic asthma, airborne allergens trigger lung inflammation and airway narrowing, causing symptoms like wheezing and shortness of breath. 

Skin. Reactions to plants (poison ivy, poison oak, poison sumac, chrysanthemums), metals (nickel: jewelry, buckles; cobalt), latex (rubber gloves, balloons, shoes), chemicals (formaldehyde, adhesives, dyes, cleaning agents), fragrances and preservatives (perfumes, soaps, cosmetics, moisturizers, hair products), and cosmetics (makeup, nail polish) can cause itchy rashes or swelling.  Atopic dermatitis, an allergic skin condition also called eczema, can cause skin to itch, form red or brown patches that may be harder to see on darker skin tones, or flake, peel, or crack.

Food. Immune response to proteins in foods (peanuts, eggs, milk, shellfish, etc.), can cause hives, swelling, or life-threatening anaphylaxis. See below.

Medication.  Reactions to medications (like penicillin, NSAIDs: aspirin, ibuprofen, naproxen) can manifest as facial swelling, rashes, hives, breathing issues, vomiting or diarrhea, or feeling dizzy.  Reactions can be hard to pinpoint and may be confused with side effects.

Chemotherapy can make your skin much more sensitive, increasing the likelihood of developing an allergic or irritant reaction to bandage adhesives, manifesting as redness, itching, dryness, or a square-shaped rash, often due to weakened skin or immune response.

Note: Pat developed an allergy to band aid adhesives while undergoing chemotherapy.  The allergy disappeared at an unknown time after treatment.  (She was reluctant to use adhesive bandages for a while.)

Not included in the figure above are insect sting allergies from bees, wasps, or fire ants that can cause pain and a large area of swelling at the sting site, itching or hives all over the body, skin warmth and a change in skin color, cough, and chest tightness, and wheezing or shortness of breath.

Having an allergy raises the risk of certain complications, including:

Asthma. If you have an allergy, you're more likely to have asthma, an immune system reaction that affects the airways and breathing.  Often, asthma is triggered by exposure to allergens in the environment.

Infections. Your risk of getting infected sinuses, ears, or lungs is higher if you have hay fever or asthma.

Anaphylaxis. Anaphylaxis is a severe, sudden, and potentially life-threatening allergic reaction, causing widespread body symptoms like airway constriction, swelling, hives, and a dangerous drop in blood pressure (shock).  Triggers include foods, insect stings, medications, and latex.  Anaphylaxis requires immediate treatment with epinephrine (adrenaline) to reverse symptoms and prevent fatality, with a trip to the ER necessary afterward.

You generally have to be exposed to a substance more than once before you’ll react to it.  The first time you’re exposed, your body sees it as foreign and creates antibodies to it (sensitization).  The next time you’re exposed to the same substance, it activates the antibodies.  This alerts your immune system to attack, triggering your symptoms.

Your allergies will continue as long as you’re exposed to the allergen. Some start within minutes of exposure, while others don’t start until hours or days later.  Once you’re no longer around allergens, your symptoms should go away after a few hours.  Some allergies, like poison ivy rashes, can last for a few weeks.

The tendency to have allergies often runs in families.  Whether or not someone develops an allergy will depend on various things, including environmental factors.  Allergies and related conditions such as asthma may be more likely to develop in people who are exposed to air pollution and cigarette smoke, for instance.

Allergies usually start in childhood or puberty, and often don't go away.  Some allergies can get better in adulthood, though.  For instance, certain food allergies (e.g. allergies to milk or chicken eggs) may disappear.  Whether or not an allergy can get better depends on what triggers it.

Allergy symptoms are often mild at first and then become more severe over time.  They sometimes lead to other medical conditions.  If people have hay fever for many years, the allergy might “move down” into the lower airways (lungs) too, causing asthma.  Allergies can also increase the likelihood of developing eczema.

People who are allergic to pollen might also be allergic to certain foods.  This is known as "cross-reactivity."  It occurs because the different allergens have similar proteins in them, and the immune system reacts to both.

More on Food Allergies

A wide variety of foods can cause allergic reactions, but 90% of allergic responses to foods are caused by cow's milk, soy, eggs, wheat, peanuts, tree nuts (pecans, pistachios, and walnuts), fish, and shellfish. The most common food allergy in the U.S. population is a sensitivity to crustacea (crabs, lobsters, prawns, scampi).  

The figure below identifies common food allergies:

Common food allergies.

Rates of food allergies differ between adults and children.  Children can sometimes outgrow peanut allergies.  Egg allergies affect one to two percent of children but are outgrown by about two-thirds of children by the age of five.  

Note:  My 15-month-old great grandson has been diagnosed with egg and peanut allergies.  He is currently undergoing desensitization treatment.

Milk-protein allergies - distinct from lactose intolerance - are most common in children.  Some people are unable to tolerate milk from goats or sheep as well as from cows, and many are also unable to tolerate dairy products such as cheese.  Roughly 10% of children with a milk allergy will have a reaction to beef.  Lactose intolerance, a common reaction to milk, is not a form of allergy at all, but due to the absence of an enzyme in the digestive tract.

Seeds, including sesame seeds and poppy seeds, contain oils in which protein is present, which may elicit an allergic reaction.

A food allergy can cause tingling in the mouth; swelling of the lips, tongue, face, or throat; itchy welts (hives); stuffy nose, sneezing or teary eyes that itch; stomach cramps; vomiting or diarrhea; and in severe cases anaphylaxis.

 

Diagnosis

Allergy diagnosis involves a doctor taking your medical history and using tests like skin prick/scratch tests or blood tests to identify triggers for reactions like food, pollen, or pet allergies, with further tests like patch tests or pulmonary function tests used as needed.  The goal is to pinpoint allergens causing symptoms like sneezing, hives, or breathing issues, guiding treatment.  

Common Diagnostic Methods:

Skin Prick/Scratch Test. The most common test, where drops of allergens are placed on skin (forearm/back) and lightly pricked; redness and hives indicate sensitivity within 15 minutes. 

Skin test for allergies.

Intradermal Skin Test. An allergen is injected under the skin's surface; used if prick tests are negative but allergies are suspected. 

Blood Test. Measures antibodies in your blood due to allergens; useful if skin tests aren't possible. 

Patch Test. Patches with potential triggers are applied to your back for days to check for delayed skin reactions (contact dermatitis). 

Nasal Smear. Examines nasal secretions for signs of inflammation. 

Pulmonary Function Test. Measures lung function to help diagnose asthma linked to allergies. 

Food Challenge Test. The most definitive procedure for accurately diagnosing or ruling out a food allergy.  It involves consuming gradually increasing amounts of a suspected allergen under strict medical supervision in a clinical setting. 

 

Management/Treatment

When to See a Doctor. Talk to a healthcare provider if you have symptoms of allergies and want to get to the bottom of what’s causing them.  A primary care provider might refer you to a specialist, like an allergist or dermatologist, to get certain tests (see above).

Go to the ER or call 911 if you experience:

• Swelling of your face, lips, tongue, or throat
• Difficulty breathing
• Chest pain or tightness
• Hives all over your body
• Tingling hands, feet, or lips
• Feeling weak, dizzy, or faint
• Feeling of dread or impending doom

If you have an allergy that could cause a severe reaction, your provider will recommend you carry an epinephrine auto-injector to use at the first signs of a severe allergic reaction.

Approaches to Avoid or Help Relieve Allergy Symptoms.

Avoid Contact with Allergens. How well this works will mainly depend on the type of trigger.  It is usually quite easy to avoid contact with things like certain foods or chemical substances.  It is almost impossible to avoid pollen, though.  But pollen calendars and forecasts (for instance, on the internet or on weather apps) can give you an idea of the pollen count in certain regions.   Keep your windows closed during pollen season.

People with dust mite allergies can somewhat lower their exposure to dust mites in their home by taking precautions such as cleaning regularly, using a mite-proof mattress cover, and removing "dust traps." Avoid touching or getting licked by animals you’re allergic to, and change your clothes after you’ve been around them (don’t allow them in your bedroom or on your furniture, and don’t touch their toys). 

If you have a food allergy, check food labels, keep allergen-free foods in your house, and only eat at restaurants where you know you can eat something that’s allergen-free.   

Keep a diary when trying to figure out what causes your allergic symptoms or makes them worse; track your activities and what you eat.  Also note when symptoms happen and what seems to help.  This may help you and your healthcare professional find your triggers.

Medication. Antihistamines or steroids are often used, especially for hay fever and allergic conjunctivitis (an allergy-related eye inflammation). These medications are available in various forms, including tablets, nasal sprays, and injections.  Steroid lotions or creams can be used to treat allergic skin reactions.

Allergen-Specific Immunotherapy (Desensitization). A bit like with vaccines, this treatment approach involves exposing people to small amounts of the allergen.  It is done at regular intervals by either injecting the allergen under your skin or placing it under your tongue in the form of a tablet or drops.  It takes at least three to five years to complete allergen-specific immunotherapy.  This approach is mainly used for the treatment of allergies to pollen (hay fever), dust mites, and insect venom.

If you’re still having bothersome allergy symptoms even with treatment, you might get some relief with:

• Oral decongestants or saline rinses for nasal symptoms
• A cold washcloth or eye drops made for allergies to help relieve itchy eyes
• Showering and putting on fresh clothes to help remove lingering allergens on your body
• Hypoallergenic or fragrance-free lotions to help calm itchy rashes

 

 Interesting Facts

1.       Today, allergies are the sixth leading cause of chronic illness in the United States, costing around $18 billion a year. 

2.       More than 100 million people in the U.S. experience various types of allergies each year.  Common examples include seasonal allergies, eczema, and food allergies.

3.       Allergic conditions are one of the most common health issues affecting children in the U.S. 

4.       On average, it is estimated that anaphylaxis results in 45,000-50,000 emergency room visits in the United States each year.

5.       In 2021, approximately 81 million people in the U.S. were diagnosed with seasonal hay fever. This equals around 26% (67 million) of adults and 19% (14 million) of children.

6.       As of 2021, about 20 million people have food allergies in the U.S.

7.       Adverse drug reactions account for 3 - 6% of all hospital admissions in the United States.

8.       The most reported drug allergy is to penicillin, with up to 10% of people saying they are allergic to this type of drug. 

9.       Insect sting allergies affect about 3% of the U.S. population.

10.   In the United States, between 2011 - 2021, there were a total of 788 deaths from hornet, wasp, and bee stings. 

 

 Sources

My principal sources include: “Allergy,” wikipedia.com; “History of allergies,” fondation-ipsen.org; “A History of Allergies,” achooallergy.com; “Allergies: Types, Symptoms, Treatment and Management,” my.clevelandclinic.com; “Allergies - Symptoms and Causes,” mayoclinic.org; “Allergy Facts” aafa.org/allergies/allergy-facts/; plus, numerous other online sources, including answers to many queries using Google in AI-Mode.