Each person has an immune (defence) system. An immune system is made up of special cells that attack and destroy bacteria, viruses, fungi or poisons that enter the body and try to harm it. If any of these substances (antigens) get into the body, the immune cells recognize them, and make other immune cells release chemicals to destroy them. One of these chemicals is called histamine.
If you have an allergy, you have antibodies that react against these substances. These substances are called allergens, and are normally harmless. They include pollen, house dust, molds or animal dander. When your body is exposed to an allergen, many chemicals, including histamine, are released. It is this burst of histamine which will cause symptoms such as itchy, watery eyes, runny nose, nasal congestion, sneezing, sore throat, swollen eyes or headaches.
For most people these are familiar symptoms. The common cold has very similar symptoms, but there are some significant differences between these two conditions.
|Time frame||Weeks or months||About a week|
|Sneezing||Common||Uncommon, except at early stages|
|Congestion||Common||Nasal and sinus congestion is common|
|Nasal discharge||Usually clear and thin||At first clear and watery, but may turn thick and yellow or green|
|Sore throat||May occur - often due to mouth breathing||May occur|
|Change of location||May relieve symptoms||No help at all|
Even though people can be allergic to many different things, allergens can be put into three different groups.
Some allergens affect people all year round. Examples are dust, molds and animal dander. People with perennial allergies develop more symptoms when they are exposed to more of the allergen. The symptoms caused by these allergens are the same as those caused by the seasonal allergens.
This is often referred to as 'hay fever.' It usually occurs at the same time each year. It may correspond to the pollen seasons, which vary according to the different types of pollen (i.e. grass, trees, or weeds) and the geographic location.
Skin Allergies or Insect Stings
These allergens will not be discussed in this article. Please ask to your doctor or pharmacist for more information.
There may not be a cure for the symptoms of an allergy, but steps can be taken to lessen the discomfort.
This can be done in one of two ways. First, when an allergic reaction occurs, keep a mental note of where the person is and what is around them. Over time, the cause of the reaction may become obvious. If the person cannot pinpoint the allergens that are causing the allergic reactions, visit the doctor. Skin tests may pinpoint specific allergens.
Once the allergen is known, try to avoid it or limit exposure to it. However, this is not always easy. For example, if a pet is causing the allergy, remove the pet from the house. If there is no easy solution, changes to the home surroundings can reduce the symptoms.
If a person still suffers from symptoms despite attempts to change the environment, medications are available to help. Remember, the symptoms of an allergy are caused when a chemical called histamine is released in the body during an exposure to an allergen. Antihistamines are medications that block the action of the histamine and can be used to reduce the seriousness of the symptoms. Antihistamines are more effective in preventing histamine’s response than in reversing it. For a seasonal allergy, start taking the antihistamine one to two weeks before the start of the season. Continue taking the medication regularly until the end of the season, even if your symptoms improve. For a perennial allergy, take the antihistamine two to five hours before coming in contact with the allergen.
There are two different classes of antihistamines - classic (older, first generation) and non-classic (newer, second generation). The two groups are equally as effective (about 70 to 85 per cent) in relieving the symptoms of itchy watery eyes, nasal itching, runny nose and sneezing. Most of the antihistamines will bring peak relief within two to three hours. The differences between the two classes are in how long they work, the side effects they produce and their cost. Side effects will often disappear with continued use and are rarely serious.
Some examples of the common classic antihistamines are brompheniramine, chlorpheniramine, diphenhydramine, triprolidine, and clemastine. These can start to relieve symptoms within 15 to 30 minutes, and will typically bring relief for three to six hours. There are long-acting or sustained release products which may bring relief for a longer period of time. The most common side effect is drowsiness, which can range from a small effect to a deep sleep. Although sedation may be desirable for use at night, this can be a hazard for daytime activities that require alertness and coordination. However, most people who become drowsy find that this is no longer a problem within the first few days of using the medication. Since alcohol and other medications can also cause drowsiness, using these with antihistamines can increase the drowsiness. Speak with your doctor or pharmacist about taking antihistamines with other medications.
Classic antihistamines may cause some people to become restless, nervous, have difficulty with sleeping or experience shaking. Unlike sedation, these side effects may be more serious and should be discussed with your doctor or pharmacist should they occur while taking the drug. Other side effects that may occur while taking classic antihistamines are stomach upset, nausea or vomiting. Any side effect may be decreased if the antihistamine is taken with food or a full glass of water or milk. Dry mouth, an increase in appetite, constipation or diarrhea may also occur.
Patients who have an enlarged prostate, glaucoma, or heart disease should check with their doctor before taking classic antihistamines. These drugs can cause bladder problems, blurred vision or a rapid heart beat. The non-classic antihistamines may be a good choice for anyone with the above problems.
Some examples of non-classic antihistamines include loratadine, cetirizine, and fexofenadine. They can relieve symptoms for up to 24 hours and have minimal side effects. Most of them are non-drowsy. This is an important consideration if you need to drive or perform any tasks that require alertness..
A stuffy nose is often a common symptom of an allergy sufferer. To combat the stuffy nose, a decongestant may be used with an antihistamine. The decongestant helps to keep the passages to the sinuses (hollow spaces in the bone around the nose) open and make breathing easier. Some examples are oxymetazoline, xylometazoline, and pseudoephedrine.
Decongestants are available in several different forms - nasal sprays, tablets, capsules or liquids. It is important to note that sprays should not be used longer than three to five days in a row because “rebound congestion” can occur. This means that the person will tend to use the spray more often with less of a response. This does not occur with the tablets, liquids or capsules. Each form has good and bad points.
Decongestant tablets may cause problems for people with uncontrolled high blood pressure, heart problems, glaucoma, diabetes, or an over-active thyroid. They can also cause difficulty for people on certain medications for depression. Before using a decongestant, any allergy sufferer should be advised to talk with their doctor or pharmacist about the safety of their use.
Saline nasal solutions can also be used to provide relief for a stuffy nose. The saline solutions can moisturize the nasal lining, make the “stuffiness” liquid, and wash away any allergens. These drops or sprays can be used on a regular basis or only if needed.
Other tips for relieving stuffy noses include:
Choosing the proper medication is important as an allergy sufferer may need to take it for a long period of time. Different medications are available and several may need to be tried before the most suitable is found. It may happen that a medication at recommended doses does not provide adequate relief. If this is the case, a drug from a different class may need to be tried. The selection of any medication rests on achieving a balance between desired symptom relief and undesired side effects.
There are other treatments available for those who do not get relief with any of the non-prescription therapies, or cannot tolerate the side effects. Ask your doctor or pharmacist for further information about these treatments.
Although there is no cure for allergies, there are several ways to cope. First, determine if it is an allergy, then try to identify the allergen. Symptoms can be decreased through environmental controls or by taking non-prescription medications. Ask your doctor or pharmacist for advice in helping to choose what is best for you.