Harold Kaiser (Practicing Allergist and Clinical Professor of Medicine, University of Minnesota Medical School) gives expert video advice on: What causes allergies?; What happens in my body when I have an allergic reaction?; Are allergies becoming more common? and more...
What is an "allergen"?
An allergen is a substance that evokes an allergic response. In other words, if I'm not allergic to peanuts and I eat some peanuts, I eat some peanuts. If you are allergic to peanuts and you eat some peanuts, then your body reacts with a big reaction: inflammation, rash, shortness of breath, different things like that. An allergen is essentially an atypical, unusual response to something that people normally have no problems with. There is a thought that the word "allergy" derives from a Greek word "allos" meaning atypical or unusual. You're getting an atypical, unusual reaction to something that doesn't bother everybody.
What causes allergies?
The causes of allergies are complex. There's a genetic potential and then an exposure which are necessary. In other words, a two hit thing. If you have the potential to become allergic to ragweed and you live in California where there is no ragweed, you will not manifest allergic reactions. If you live in the Midwest and you have the potential, then your exposure to ragweed may or may not cause an allergic reaction. We don't know why some people have the potential to go on to develop allergies and others don't. But, the two necessary things in causing allergies are the genetic potential which you've inherited and the exposure. Also, repeated exposure is often necessary.
What happens in my body when I have an allergic reaction?
When you have an allergic reaction, the body has a certain immune response. In other words, as a result of your exposure to whatever it is you're allergic to, there starts a cascade of immunological and biochemical events, which results in the secretion by the blood cells, the T-cells and the B-cells of chemicals with funny names like chemokines, and leukotrienes, and cytokines, and histamine. These manifest, which causes the allergic reaction - the swelling, the itching, the redness, the coughing or the wheezing.
Are allergies becoming more common?
Allergies are becoming more prevalent and common. The reason for this increase is not quite established. There are several theories as to why allergies are becoming more common. First of all, the diagnosis process is better. Secondly, patients are becoming more aware of allergies, and they report things that they might have previously suspected as a cold or the flu, but now think of allergies as part of the problem. Also, our lives have changed. More people are living urban lives, coming under exposure to dust and dust mites, and things that are in buildings are potentially causing a problem. There's another issue called the Hygeine Hypothesis. As a result of our cleaner living, our antibiotics in childhood, our immunization, the fact that we don't come into contact with as much dirt as we would if we lived more rural lives, allergies are becoming more common and all this may in some way not allow the body to develop the potential immunologic defenses to prevent allergies, so allergies develop. It's an attractive theory, the science is not quite rigorous yet, but it's one of the reasons people think allergies are becoming more common.
What are the most common types of allergies?
The most common types of allergies are allergic rhinitis, or hay fever; allergic asthma; allergic skin disease and hives; drug allergies; and food allergies. Less common allergies might include reactions to stinging insects, reactions to the environment, and the like.
What is "contact dermatitis"?
Contact dermatitis is a skin reaction, an allergic reaction where the skin reacts to a substance with which it comes into contact. This is a simple explanation of what contact dermatitis is. Poison Ivy, for example, is a contact dermatitis. If you are a susceptible person and you are exposed to Poison Ivy, you will get a rash. Some people get contact dermatitis from things like detergents when they wash their clothes with detergents with enzymes or coloring agents. Some people get contact dermatitis through their clothes. Contact dermatitis is a skin reaction to something which they come into contact with.
What are "skin allergies"?
Skin allergies are allergic reactions to the skin. They may be from something you ingest, like a food or a medication. A skin allergy may be from a contact reaction; that is, the skin will become allergic or reactive to something with which you come into contact. In other words, allergic reactions generally occur where mucous membranes are secreted: the eyes, the nose, the sinuses, the throat, and in the lungs. It also can occur in the skin.
If I have nasal congestion, do I have allergies?
No, nasal congestion is not always an allergy. For example, a cold is a nasal congestion- that's rhinitis, infectious rhinitis, viral infectious rhinitis. A fancy way of saying that you have inflammation in your nose because you have a cold. On the other hand, people who inhale things to which they are allergic, such as ragweed in the Midwest, or grass palm on the west coast, or people who have a reaction or [are] allergic to their animals, get inflammation in the nose. Sneezing, itchy nose, mucous secretions, and the like, that's a nasal allergy. There're also non-allergic forms of rhinitis, where people simply have a nose which runs or is stuffy much of the time, even though there is no known allergy. All rhinitis is not allergic, a fraction of it is.
Can allergies be life threatening?
Penicillin allergy is a common form of drug allergy and there are deaths reported every year from reactions to penicillin. Peanut allergy gets a lot of publicity now and there are deaths from peanut allergy reported every year. Severe allergic reactions can be life threatening and there are deaths every year from anaphylactic reactions, which can be allergic or not allergic. But to answer the question, they are rarely life-threatening, but we take them seriously.
What is "rhinitis"?
Rhinitis is another word for inflammation of the nose. Rhinitis can be allergice, non-allergic, infectious, related to irritation and the like. The symptoms tend to be a stuffy and runny nose, excess mucus production, and a feeling of congestion in the nose.
How is rhinitis treated?
Rhinitis is treated differently depending on the cause. In other words if you have a cold one might treat rhinitis with aspirin, hot soup, rest, and whatever you do it will disappear in about a week. Allergic rhinitis will require treatment by avoidance, by medication, and if avoidance or medication don't do the proper job, allergy injections are a potential help in the future. There are a lot of medications that are valuable for the symptomatic treatment of rhinitis - it's a common entity and it's often easily treated. Sometimes the frustration of rhinitis is tremendous. It's not a trivial problem especially to the patient who has it.
What is "sinusitis"?
Sinusitis is inflammation of the sinuses. The sinuses are the cavities behind our cheeks and behind our forehead which help to make up the skull. They're lined with mucus secreting membranes and when these membranes become infected or inflamed, there's congestion and this congestion can lead to a block which leads to sinusitis - inflammation of the sinuses.
What is an "antibody"?
An antibody is the body's response to an immunogen or an antigen. By that, I mean, if you ingest or inhale or acquire something that is foreign to you, your body sets up a defense system. The body manufactures antibodies which help to fight this. This can occur in diseases such as measles or mumps or chicken pox and it can occur as a result of immunization or vaccination for these things. It can also occur in allergic diseases when the patient is exposed to an allergen, something that causes an allergic reaction. The body then forms antibodies to help to shut down this allergic reaction. It's a long-winded explanation and it's over-simplified, but antibodies help the body fight infection or inflammation.
What is "immunoglobulin E" or "IgE"?
Immunoglobulin E is the immunoglobulin, the body chemical, which is thought to be important in the cause of many allergic reactions. For example, patients who does not have allergics may have a level of immunoglobulin E. A patient who has an allergic condition, such as allergic rhinitis, or allergic asthma may have a very high elevated level of immunoglobulin E. It's an antibody that can be measured in the laboratory, and gives a measure of how allergical reactive that patient might be. And, it's also is the substance that causes the allergic skin test. If you ever seen someone who has allergic skin testing they get a flare reaction, and a red reaction. And, if they're responding to the substance, let's say, that has been tested. Immunoglobulin E is the body chemical that causes the allergic reaction.