An allergic reaction involves two features of the human immune response. One is the production of immunoglobulin E (IgE), a type of protein called an antibody that circulates through the blood. The other is the mast cell, a specific cell that occurs in all body tissues but is especially common in areas of the body that are typical sites of allergic reactions, including the nose and throat, lungs, skin, and gastrointestinal tract.
The ability of a given individual to form IgE against something as benign as food is an inherited predisposition. Generally, such people come from families in which allergies are common—not necessarily food allergies but perhaps hay fever, asthma, or hives. Someone with two allergic parents is more likely to develop food allergies than someone with one allergic parent.
Before an allergic reaction can occur, a person who is predisposed to form IgE to foods first has to be exposed to the food. As this food is digested, it triggers certain cells to produce specific IgE in large amounts. The IgE is then released and attaches to the surface of mast cells. The next time the person eats that food, it interacts with specific IgE on the surface of the mast cells and triggers the cells to release chemicals such as histamine. Depending upon the tissue in which they are released, these chemicals will cause a person to have various symptoms of food allergy. If the mast cells release chemicals in the ears, nose, and throat, a person may feel an itching in the mouth and may have trouble breathing or swallowing. If the affected mast cells are in the gastrointestinal tract, the person may have abdominal pain or diarrhea. The chemicals released by skin mast cells, in contrast, can prompt hives.
Food allergens (the food fragments responsible for an allergic reaction) are proteins within the food that usually are not broken down by the heat of cooking or by stomach acids or enzymes that digest food. As a result, they survive to cross the gastrointestinal lining, enter the bloodstream, and go to target organs, causing allergic reactions throughout the body.
The complex process of digestion affects the timing and the location of a reaction. If people are allergic to a particular food, for example, they may first experience itching in the mouth as they start to eat the food. After the food is digested in the stomach, abdominal symptoms such as vomiting, diarrhea, or pain may start. When the food allergens enter and travel through the bloodstream, they can cause a drop in blood pressure. As the allergens reach the skin, they can induce hives or eczema, or when they reach the lungs, they may cause asthma. All of this takes place within a few minutes to an hour.
Drug-Medication Allergies (Drug Allergies)
Drug allergies are a group of symptoms caused by allergic reaction to a drug (medication).
Drug/Medication Allergies -Anti-seizure drugs
Many seizure disorders are controlled by various types of anti-seizure medications (sometimes called anti-convulsants or anti-seizure drugs [AEDs]). As well, different types of seizures require different medications. Epilepsy medication may be prescribed alone or in combination. If a person has more than one type of seizure, s/he may have to take more than one type of drug to gain control. Reaction to a given drug varies from one person to the next. Medication that works for one person with epilepsy will not necessarily work for another
Drug/Medication Allergies –Insulin
There are some people who have allergic reactions to insulin. This tended to be more common when insulin was prepared from animals and was not as pure as it is now. The insulin currently used is mostly identical to human insulin. Only very rarely are people allergic to the solutions in which the insulin comes. Sometimes there is an allergy to the insulin molecule itself. Generally the allergy starts by causing itchy feelings around the site of the injection
Drug/Medication Allergies -Local anesthetics
Fortunately, true allergic reaction to local anaesthetic is rare. However, adverse reactions (local anaesthetic overdose, fainting) appear to be common. Some anesthetic drugs trigger cross-allergies, particularly in persons who have allergies to eggs and soy products.
Drug/Medication Allergies -Penicillin-related antibiotics
Penicillin allergy is the most common drug allergy. Allergic reactions occur because your immune system responds to the drug as if it were a harmful substance instead of a helpful remedy. For reasons not fully understood, your body creates antibodies called immunoglobulin to attack the medication. In most cases of penicillin allergy, the type of immunoglobulin that causes the most problems is type E (IgE).
Drug/Medication Allergies -Sulfa drugs
Sulfa drugs are used to treat bacterial infections, although they have largely been replaced for this purpose by antibiotics; some are also used in the treatment of diabetes. Because sulfa drugs were first used to elucidate ways in which substances can interfere with the metabolism of invading microorganisms, they are of historical interest.
Dust Mites Allergies
Dust mites are tiny organisms, distantly related to spiders. You can't see them with the naked eye. Other than allergies, they don't cause any harm. They like to live in areas that are warm and humid, and they can be found in many homes. Some people are allergic to dust mites' decayed bodies and fecal material, which become components of airborne household dust. Dust mite allergen can also trigger an asthma attack.
In adults, the most common foods to cause allergic reactions include: shellfish such as shrimp, crayfish, lobster, and crab; peanuts, a legume that is one of the chief foods to cause severe anaphylaxis, a sudden drop in blood pressure that can be fatal if not treated quickly; tree nuts such as walnuts; fish; and eggs.
In children, the pattern is somewhat different. The most common food allergens that cause problems in children are eggs, milk, and peanuts. Adults usually do not lose their allergies, but children can sometimes outgrow them. Children are more likely to outgrow allergies to milk or soy than allergies to peanuts, fish, or shrimp.
The foods that adults or children react to are those foods they eat often. In Japan, for example, rice allergy is more frequent. In Scandinavia, codfish allergy is more common.
Hayfever/Pollen and Mold
Hay fever is a commonly used term for pollen allergy, a type of seasonal allergic rhinitis (runny nose). Pollen grains can be dispersed into the air in the spring, summer and fall, depending on the type of tree, grass or weed. For example, ragweed is a common cause of pollen allergy reactions in the fall. In mild climates, some plants pollinate in the winter as well. People inherit a tendency to be allergic, meaning an increased likelihood of being allergic to one or more allergens (such as pollen), although they probably do not inherit a tendency to be allergic to any specific allergens. Children are much more likely to develop allergies if their parents have allergies, even if only one parent is allergic.
Exposure to allergens at certain times when the body's defenses are lowered or weakened, such as after a viral infection or during pregnancy, also seems to contribute to the development of allergies. Plain-looking trees, grasses and weeds, which do not have showy flowers, produce the types of pollen that most commonly cause allergic reactions. These plants manufacture small, light, dry pollen granules that are custom-made for wind transport. Although most allergenic pollen comes from plants that produce it in huge quantities, it's the chemical makeup of the pollen that determines whether it is likely to cause hay fever.
Generally, pollen is most abundant in the early morning, especially between 5:00 a.m. and 10:00 a.m. Other considerations, however, also determine exposure, such as wind velocity. Also, rain can wash pollen out of the air for a time, and some plants may not pollinate in damp weather. A doctor can use a skin test to see if you will react to specific pollen allergens. A diluted extract is injected under the patient's skin or is applied to a tiny scratch or puncture made on the arm or back. Skin testing is the most common method used to test for allergic reactions. Blood tests are also available to determine if you have a pollen allergy. The best treatment for pollen allergy is to avoid coming into contact with pollen. Because that is usually not possible, certain medications can control allergic reactions in most people. Several oral antihistamine medications are available over-the-counter or by a doctor's prescription. Topical nasal steroid sprays are anti-inflammatory drugs that stop the allergic rhinitis. Using a combination of antihistamines and nasal steroids can effectively treat allergic symptoms, especially in people with moderate or severe allergic symptoms.
Lactose intolerance is the inability to digest significant amounts of lactose, the predominant sugar of milk. This inability results from a shortage of the enzyme lactase, which is normally produced by the cells that line the small intestine. Lactase breaks down milk sugar into simpler forms that can then be absorbed into the bloodstream. When there is not enough lactase to digest the amount of lactose consumed, the results, although not usually dangerous, may be very distressing. While not all persons deficient in lactase have symptoms, those who do are considered to be lactose intolerant. Common symptoms include nausea, cramps, bloating, gas, and diarrhea, which begin about 30 minutes to 2 hours after eating or drinking foods containing lactose. The severity of symptoms varies depending on the amount of lactose each individual can tolerate.
Some causes of lactose intolerance are well known. For instance, certain digestive diseases and injuries to the small intestine can reduce the amount of enzymes produced. In rare cases, children are born without the ability to produce lactase. For most people, though, lactase deficiency is a condition that develops naturally over time. After about the age of 2 years, the body begins to produce less lactase. However, many people may not experience symptoms until they are much older.
Between 30 and 50 million Americans are lactose intolerant. Certain ethnic and racial populations are more widely affected than others. As many as 75 percent of all African Americans and American Indians and 90 percent of Asian Americans are lactose intolerant. The condition is least common among persons of northern European descent.
Researchers have identified a genetic variation associated with lactose intolerance; this discovery may be useful in developing a diagnostic test to identify people with this condition.
The most common tests used to measure the absorption of lactose in the digestive system are the lactose tolerance test, the hydrogen breath test, and the stool acidity test. These tests are performed on an outpatient basis at a hospital, clinic, or doctor's office.
The lactose tolerance test begins with the individual fasting (not eating) before the test and then drinking a liquid that contains lactose. Several blood samples are taken over a 2-hour period to measure the person's blood glucose (blood sugar) level, which indicates how well the body is able to digest lactose.
Normally, when lactose reaches the digestive system, the lactase enzyme breaks it down into glucose and galactose. The liver then changes the galactose into glucose, which enters the bloodstream and raises the person's blood glucose level. If lactose is incompletely broken down, the blood glucose level does not rise and a diagnosis of lactose intolerance is confirmed.
The hydrogen breath test measures the amount of hydrogen in a person's breath. Normally, very little hydrogen is detectable. However, undigested lactose in the colon is fermented by bacteria, and various gases, including hydrogen, are produced. The hydrogen is absorbed from the intestines, carried through the bloodstream to the lungs, and exhaled. In the test, the patient drinks a lactose-loaded beverage, and the breath is analyzed at regular intervals. Raised levels of hydrogen in the breath indicate improper digestion of lactose. Certain foods, medications, and cigarettes can affect the accuracy of the test and should be avoided before taking it. This test is available for children and adults.
The lactose tolerance and hydrogen breath tests are not given to infants and very young children who are suspected of having lactose intolerance. A large lactose load may be dangerous for the very young because they are more prone to the dehydration that can result from diarrhea caused by the lactose. If a baby or young child is experiencing symptoms of lactose intolerance, many pediatricians simply recommend changing from cow's milk to soy formula and waiting for symptoms to abate.
If necessary, a stool acidity test, which measures the amount of acid in the stool, may be given to infants and young children. Undigested lactose fermented by bacteria in the colon creates lactic acid and other short-chain fatty acids that can be detected in a stool sample. In addition, glucose may be present in the sample as a result of unabsorbed lactose in the colon.
Fortunately, lactose intolerance is relatively easy to treat. No treatment can improve the body's ability to produce lactase, but symptoms can be controlled through diet.
Young children with lactase deficiency should not eat any foods containing lactose. Most older children and adults need not avoid lactose completely, but people differ in the amounts and types of foods they can handle. For example, one person may have symptoms after drinking a small glass of milk, while another can drink one glass but not two. Others may be able to manage ice cream and aged cheeses, such as cheddar and Swiss, but not other dairy products. Dietary control of lactose intolerance depends on people learning through trial and error how much lactose they can handle.
For those who react to very small amounts of lactose or have trouble limiting their intake of foods that contain it, lactase enzymes are available without a prescription to help people digest foods that contain lactose. The tablets are taken with the first bite of dairy food. Lactase enzyme is also available as a liquid. Adding a few drops of the enzyme will convert the lactose in milk or cream, making it more digestible for people with lactose intolerance.
Lactose-reduced milk and other products are available at most supermarkets. The milk contains all of the nutrients found in regular milk and remains fresh for about the same length of time, or longer if it is super-pasteurized.
Allergy to latex was first recognized in the late 1970s. Since then, it has become a major health concern as an increasing number of people in the work place have been affected. Health care workers exposed to latex gloves or medical products containing latex are especially at risk. It is estimated that 8-12% of health care workers are latex sensitive. Between 1988-1992, the Federal Drug Administration (FDA) received more than 1000 reports of adverse health effects from exposure to latex, including 15 deaths due to such exposure.
As used in this discussion, latex refers to the natural rubber latex manufactured from a milky fluid that is primarily obtained from the rubber tree (Hevea brasiliensis). Some synthetic rubber materials may be referred to as "latex" but they do not contain the protein that produces latex allergy.
Any animal with fur or feathers can contribute to your allergies. If you're in close contact with such an animal and you're sensitive to the allergens it gives off, that animal can give you allergy symptoms. The most common pet allergy comes from cats. When you're allergic to cats, you aren't actually allergic to their hair. Rather, cat allergies come from cat dander — flaky skin cells and dried saliva. Dogs also have dander that can trigger allergies, though this is not as common a problem as it is with cats.
Links to Allergies
- All About Allergies: A wealth of information, links and resources.
- The Food Allergy and Anaphylaxis Network: The mission of this network is to raise public awareness, to provide advocacy and education, and to advance research on behalf of all those affected by food allergies and anaphylaxis.
- Allergy and Asthma Resouces list: An extensive list of resources, associations, organizations and other information on these topics.
- Allergy statistics
- Sinusitis: extensive information on this topic
- The Guide to Allergies and Asthma: An extensive resource of information on all areas of allergies and asthma concerns.