As we know allergies, also known as allergic infections or diseases, are a various number of conditions caused by hypersensitivity of the immune system to something in the environment that usually causes little or no problem in most people. These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis.In this types of infection symptoms may include red eyes, an itchy rash, sneezing, frequent runny nose, shortness of breath, or swelling. Apart from this food intolerances and food poisoning are separate conditions.
Sometimes common allergens include pollen and certain food.Metals and other substances may also cause problems. Food, insect stings, and medications are common causes of severe reactions.Their development is due to both genetic and environmental factors.The underlying mechanism involves immunoglobulin E antibodies (IgE), part of the body's immune system, binding to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine. Diagnosis for the treatment is typically based on a person's medical history.Further testing of the skin or blood may be useful in certain cases.Positive tests, however, may not mean there is a significant allergy to the substance in question.
Early exposure to potential allergens may be protective. Treatments for allergies include avoiding known allergens and the use of medications such as steroids and antihistamines.In severe reactions injectable adrenaline (epinephrine) is recommended.Allergen immunotherapy, which gradually exposes people to larger and larger amounts of allergen, is useful for some types of allergies such as hay fever and reactions to insect bites. Its use in food allergies is unclear.
Allergies are common.In the developed world, about 25% of people are affected by allergic rhinitis,about 7% of people have at least one food allergy, and about 210% have atopic dermatitis at some point in time. Depending on the country about 2–20% of people have asthma. Anaphylaxis occurs in between 0.06–2.3% of people.Rates of many allergic diseases appear to be increasing.
Allergies occur when your immune system reacts to a foreign substance - such as pollen, bee venom or pet dander - or a food that doesn't cause a reaction in most people.
Your immune system produces substances known as antibodies. When you have allergies, your immune system makes antibodies that identify a particular allergen as harmful, even though it isn't. When you come into contact with the allergen, your immune system's reaction can inflame your skin, sinuses, airways or digestive system.
The severity of allergies varies from person to person and can range from minor irritation to anaphylaxis - a potentially life-threatening emergency. While most allergies can't be cured, treatments can help relieve your allergy symptoms.
Food allergies are estimated to affect 5 to 7 percent of children and 6 percent of adults.
Learn about allergic skin reactions and what causes them.
People who have dust allergies are familiar with sneezing-but sneezing isn't the only uncomfortable symptom.
Stings from five insects - honeybees, hornets, wasps, yellow jackets and fire ants - are known to cause allergic reactions to the venom injected into the skin.
Pet allergies can contribute to constant allergy symptoms, such as causing your eyes to water, or causing you to start sneezing.
Learn about eye allergies, a condition that affects millions of Americans.
If you develop a rash, hives or difficulty breathing after taking certain medications, you may have a drug allergy.
If you sneeze a lot, if your nose is often runny or stuffy, or if your eyes, mouth or skin often feels itchy, you may have allergic rhinitis.
Allergic reactions to latex may be serious and can very rarely be fatal. If you have latex allergy you should limit or avoid future exposure to latex products.
Molds live everywhere-on logs and on fallen leaves, and in moist places like bathrooms and kitchens.
Sinus infection is a major health problem. It afflicts 31 million people in the United States.
Some people develop allergy symptoms when they are around cockroaches.
There is a several causes of the allergy or itching on the external part of the body.
An allergy starts when your immune system mistakes a normally harmless substance for a dangerous invader. The immune system then produces antibodies that remain on the alert for that particular allergen. When you're exposed to the allergen again, these antibodies can release a number of immune system chemicals, such as histamine, that cause allergy symptoms.
People who worked in coal mines, waste dumping yard, chemical factories, air/soil/water polluted areas are more likely to get infected with with several unknown allergy. It's mainly due to the micro parasites found in air, soil or water are main source of allergy.
You might be more likely to develop an allergy if you:
Having an allergy increases your risk of certain other medical problems, including:
Preventing allergic reactions depends on the type of allergy you have. General measures include the following:
Allergy symptoms, which depend on the substance involved, can affect your airways, sinuses and nasal passages, skin, and digestive system. Allergic reactions can range from mild to severe. In some severe cases, allergies can trigger a life-threatening reaction known as anaphylaxis.
Some types of allergies, including allergies to foods and insect stings, can trigger a severe reaction known as anaphylaxis. A life-threatening medical emergency, anaphylaxis can cause you to go into shock. Signs and symptoms of anaphylaxis include:
You might see a doctor if you have symptoms you think are caused by an allergy, and over-the-counter allergy medications don't provide enough relief. If you have symptoms after starting a new medication, call the doctor who prescribed it right away.
This is a review regarding how the allergic response of the immune system occurs and why certain people become allergic. The most common allergic diseases are described, including allergic rhinitis (nasal allergies), allergic conjunctivitis (eye allergies), allergic asthma, urticaria (hives), and food allergies.
An allergy refers to an exaggerated reaction by the immune system in response to exposure to certain foreign substances. The response is exaggerated because these foreign substances are normally seen by the body as harmless in nonallergic individuals and do not cause a response in them. In allergic individuals, the body recognizes the foreign substance, and the allergic part of the immune system generates a response.
Allergy-producing substances are called "allergens." Examples of allergens include pollens, dust mites, molds, animal proteins, foods, and medications. When an allergic individual comes in contact with an allergen, the immune system mounts a response through the IgE antibody. People who are prone to allergies are said to be allergic or "atopic."
A common scenario can help explain how allergies develop. A few months after the new cat arrives in the house, dad begins to have itchy eyes and episodes of sneezing. One of the three children develops coughing and wheezing. The mom and the other two children experience no reaction whatsoever despite the presence of the cat. How can this occur?
The immune system is the body's organized defense mechanism against foreign invaders, particularly infections. Its job is to recognize and react to these foreign substances,which are called antigens. Antigens often lead to an immune response through the production of antibodies, which are protective proteins that are specifically targeted against particular antigens. These antibodies, or immunoglobulins (IgG, IgM, and IgA), are protective and help destroy a foreign particle by attaching to its surface, thereby making it easier for other immune cells to destroy it. The allergic person however, develops a specific type of antibody called immunoglobulin E, or IgE, in response to certain normally harmless foreign substances, such as cat dander. Other antigens, such as bacteria, do not lead to production of IgE, and therefore do not cause allergic reactions. Once IgE is formed, it can recognize the antigen, such as cat dander, and can then trigger an allergic response. IgE was discovered and named in 1967 by Kimishige and Teriko Ishizaka.
In the pet cat example, the dad and the youngest daughter developed IgE antibodies in large amounts that were targeted against the cat allergen. The dad and daughter are now sensitized or prone to develop allergic reactions on repeated exposures to cat allergen. Typically, there is a period of "sensitization" ranging from days to years prior to an allergic response. Although it might occasionally appear that an allergic reaction has occurred on the first exposure to the allergen, there needs to be prior exposure in order for the immune system to react. It is important to realize that it is impossible to be allergic to something that an individual has truly never been exposed to before, though the first exposure may be subtle or unknown. The first exposure can even occur in a baby in the womb, through breast milk, or through the skin.
IgE is an antibody that all of us have in small amounts. Allergic individuals, however, generally produce IgE in larger quantities. Historically, this antibody was important in protecting us from parasites. In the example above, during a sensitization period, cat dander IgE is overproduced and coats other cells involved in the allergic response, such as mast cells and basophils, which contain various mediators, such as histamine. These cells are capable of leading to an allergic reaction on subsequent exposures to the cat allergen (cat dander). The cat protein is recognized by the IgE, leading to activation of the cells, which leads to the release of the allergic mediators mentioned above. These chemicals cause typical allergic symptoms, such as localized swelling, inflammation, itching, and mucus production. Once primed, or sensitized, the immune system is capable of mounting this exaggerated response with subsequent exposures to the allergen.
On exposure to cat dander, whereas the dad and daughter produce IgE, the mom and the other two children produce other classes of antibodies, which do not cause allergic reactions. In these nonallergic members of the family, the cat protein is eliminated uneventfully by the immune system and the cat has no effect on them.
Another part of the immune system, the T-cell, may be involved in allergic responses in the skin, as occurs from the oils of plants, such as poison ivy, poison oak, poison sumac, reactions to metal, such as nickel, or certain chemicals. The T-cell may recognize a certain allergen in a substance contacting the skin and cause an inflammatory response. This inflammatory response can cause itching, rash, and discomfort.
Allergies can develop at any age, but most food allergies begin at a young age, and many are outgrown. Environmental allergies can develop at any time. The initial exposure or sensitization period may even begin before birth. Individuals can also outgrow allergies over time. It is not fully understood why one person develops allergies and another does not, but there are several risk factors for allergic conditions. Family history, or genetics, plays a large role, with a higher risk for allergies if parents or siblings have allergies. There are numerous other risk factors for developing allergic conditions. Children born via Cesarean section have a higher risk of allergy as compared to children who are delivered vaginally. Exposure to tobacco smoke and air pollution increases the risk of allergy. Boys are more likely to be allergic than girls. Allergies are more common in westernized countries, and less common in those with a farming lifestyle. Exposures to antigens, use of antibiotics, and numerous other factors, some of which are not yet known, also contribute to the development of allergies. This complicated process continues to be an area of medical research.
The parts of the body that are prone to allergic symptoms include the eyes, nose, lungs, skin, and gastrointestinal tract. Although the various allergic diseases may appear different, they all result from an exaggerated immune response to foreign substances in sensitive individuals. The following are brief descriptions of common allergic disorders.
Allergic rhinitis ("hay fever") is the most common of the allergic diseases and refers to nasal symptoms that are due to aeroallergens. Year-round, or perennial, allergic rhinitis is usually caused by indoor allergens, such as dust mites, animal dander, or molds. Seasonal allergic rhinitis is typically caused by tree, grass, or weed pollens. Many individuals have a combination of both seasonal and perennial allergies. Symptoms result from the inflammation of the tissues that line the inside of the nose after exposure to allergens. The eyes, ears, sinuses, and throat can also be involved. The most common symptoms include the following:
Asthma is a respiratory condition that results from inflammation and hyperreactivity of the airways, leading to recurrent, reversible narrowing of the airways. Asthma can often coexist with allergic rhinitis. Other common triggers include respiratory viral infections and exercise. Common symptoms include the following:
Allergic eyes (conjunctivitis) are inflammation of the tissue layers (membranes) that cover the surface of the eyeball and the undersurface of the eyelid. The inflammation occurs as a result of an allergic reaction and may produce the following symptoms, which are generally present in both eyes:
Eczema (atopic dermatitis) is a condition commonly found in infants. It tends to occur in individuals at risk for other allergic conditions (asthma and allergic rhinitis) but is not usually caused by direct allergen exposure. The rash results from a complicated inflammatory process. Common features include the following:
Hives (urticaria) are skin reactions that appear as red, raised, itchy welts and can occur on any part of the body. Short-lived (acute) hives are often due to an allergic reaction to a food or medication, though they also commonly result from a viral infection in children. Hives that recur over a longer period of time (chronic hives) are rarely due to an allergic reaction. Hive are characterized by
Anaphylactic shock is a potentially life-threatening allergic reaction that can affect a number of organs at the same time. Allergens that typically lead to anaphylaxis are foods, medications, and venom (bee stings). Environmental allergens rarely lead to anaphylaxis. Some or all of the following symptoms may occur:
Anaphylactic shock is an emergent, life-threatening condition that occurs when blood vessels dilate excessively due to an allergic reaction, which causes a significant drop in blood pressure. This can result in inadequate blood flow to the organs in the body.
Allergens may be inhaled, ingested (eaten or swallowed), applied to the skin, or injected into the body either as a medication or inadvertently by an insect sting. The symptoms and conditions that result depend largely on the route of entry and the type of allergen.The chemical structure of allergens affects the route of exposure. Airborne pollens,for example, tend to have little effect on the skin. They are easily inhaled and will thus cause more nasal and respiratory symptoms with limited skin symptoms. When allergens are swallowed or injected, they may travel to other parts of the body and provoke symptoms that are remote from their point of entry. For example, allergens in foods may prompt the release of mediators in the skin and cause hives.
The specific protein structure is what determines the allergen's characteristics. Cat protein, Fel d 1, from the Felis domesticus(the domesticated cat), is the predominant cat allergen. Each allergen has a unique protein structure leading to its allergic characteristics.
Aside from oxygen, the air contains a wide variety of particles, including allergens. The usual diseases that result from airborne allergens are hay fever, asthma, and conjunctivitis. The following allergens can trigger allergic reactions when inhaled by sensitized individuals.
Foods and medications can also cause allergic reactions, some of which can be severe. These reactions often start with localized tingling or itching and then may lead to rash or additional symptoms, such as swelling, nausea, vomiting, diarrhea, or difficulty breathing. Here are the two most common allergens that are ingested:
Foods: The most common food allergens are cow's milk, eggs, peanuts, tree nuts, wheat, soy, shellfish, finned fish, and sesame. Cow's milk, egg, wheat, and soy allergies are most common in children and are often outgrown over time. The most common allergens in adults are peanut, tree nuts, and shellfish. It should be noted that gluten is not a common food allergy, and true gluten hypersensitivity,or celiac disease, is mediated by another type of antibody (not IgE but IgA) and also leads to a different host of symptoms (including chronic abdominal discomfort, nausea, vomiting, change in stool, anemia).
Medications: Although any medication can cause an allergic reaction, common examples include antibiotics (such as penicillin), and anti-inflammatory agents, such as aspirin and ibuprofen. Notably, many individuals who think they are allergic to medications actually can tolerate the medication without difficulty.
Contact dermatitis is an inflammation of the skin that is caused by local exposure to a substance. The majority of these localized skin reactions do not involve IgE but are caused by other inflammatory cells. A good example is poison ivy. Examples of substances that commonly cause contact dermatitis include the following:
The most severe reactions often occur when allergens are injected into the body and gain direct access to the bloodstream. This intravenous access carries the increased risk of a systemic reaction, such as anaphylaxis. The following are commonly injected allergens that can cause severe allergic reactions:
Although primary-care physicians are well equipped to treat mild allergic symptoms, allergy/immunology physicians (allergists) treat individuals with more bothersome allergies. Many allergists treat both children and adults, but some are specialized to either patient group alone.
The diagnosis of allergies begins with a detailed history and physical examination. Many people with allergies have other family members with allergic conditions. In addition to the history and exam, skin testing and sometimes blood work (specific IgE levels) can help with the diagnosis of allergies. There are several important considerations when interpreting the results of this testing:
The treatment for allergies depends on the particular condition. Some general guidelines are as follows:
Allergic rhinitis and conjunctivitis