The responses of different people towards allergic reactions differ greatly. While a number of people experience acute allergic reactions (hypersensitivity) to specific foods or insect bites, there are others who do not experience any adverse effect when they are exposed to insect bites or the same foods. Hay fever, which is attributed to an allergic reaction to inhaling grass pollen, is one of the most widespread allergic problems. When an individual inhales grass pollens it may result in swelling and inflammation of the nasal passages (allergic rhinitis) as well as watering of the eyes and nose.

Additional substances, for instance animal fur, house-dust mites, feathers, may result in the same kind of allergic reactions in people who are susceptible. Asthma is another allergic problem which may be caused by the activities of agents, except histamine. Other allergic conditions include hives (urticaria); some types of eczema, dermatitis; other rashes (at times in reaction to using any medicine) and allergic alveolitis (also known as 'farmer's lung').

Basically, allergy can be defined as a response of one's immune system to any substance that does not create problems for other people. Usually, individuals having allergies are sensitive to several things. Things that generally result in allergic reactions may include dust mites, pollens, medicines, foods, mold spores, insect stings and pet dander.

The important question is how one gets allergies. Scientists are of the view that genes as well as the environment play some role in the way one gets allergies. Usually, the immune system combats pathogenic microbes and is considered to be the defense system of our body. Nevertheless, in instance of the majority of allergic reactions, the immune system actually reacts to a fake alarm.

When an individual has allergic reactions, he/ she may experience a number of symptoms, including rashes, sneezing, runny nose, and itching, swelling and even asthma. However, the symptoms generally vary from one person to another. While allergies make one feel sick, they generally do not kill a person. Nevertheless, a serious allergic reaction known as anaphylaxis may often prove to be dangerous.


The most extensively used medications to treat allergic reactions are known as antihistamines, which can be divided into a number of sub-categories depending on their chemical structure. The action of every antihistamine sub-group somewhat differs from the other. Their characteristics are also different. The primary action of antihistamines is to neutralize the consequences of histamine - a chemical that is discharged inside the body when one gets an allergic reaction.

Histamines play a role in several functions of our body, including dilation and constriction of the blood vessels; releasing digestive enzymes into the stomach; and retrenchment of muscles of the gastrointestinal and respiratory tracts. Antihistamine medications are also called H1 blockers, as they just obstruct the activities of histamines on specific receptors, which are called H1 receptors. A different histamine group, which is called H2 blockers, is employed to treat peptic ulcers.

The majority types of antihistamines possess a notable anti-cholinergic (obstructing the impulses from the nerves) action. They are beneficial in treating an assortment of health condition. However, the use of antihistamines also results in specific unpleasant side effects.

It may be noted that antihistamine medicaments work to ease the symptoms related to allergic reaction especially when it become impossible or unfeasible to avoid coming in contact with substances that trigger the allergic reactions. Antihistamine medications are commonly used for preventing a condition called allergic rhinitis, wherein the sufferer experiences nasal as well as the upper airways inflammation owing to an allergic reaction from any substance, for instance, pollens, animal fur or house dust. Antihistamines prove to be additionally useful when they are taken just before the attack. You may not be able to notice the beneficial effects of antihistamines if they are taken when an attack is in full swing. Taking these medications after the start of an attack may also delay the beneficial actions of antihistamines.

However, the use of antihistamine medications do not prove to be useful in the case of asthma caused by comparable allergens, as the symptoms related to this allergic condition are not solely attributable to histamines. Instead, asthma caused by allergens is more likely to be a fall-out of further complicated mechanisms. In such cases, you may use antihistamines, but if they do not yield the desired results or ease the symptoms, your physician may prescribe alternative treatments.

Besides allergic reactions, antihistamine medications are effective for alleviating swelling, itching and redness as well as the typical symptoms of allergic reactions that involve the skin - for instance, infantile eczema, urticaria (hives) and different other types of dermatitis. Antihistamines may also be effective for diminishing the irritation caused by chickenpox. If you are treating the symptoms of chickenpox, antihistamine medications may either be taken orally or applied externally to the area where there is itching. When applied in the form of drops, antihistamine medications also help to lessen inflammation as well as irritation of the eyes and eyelids caused by allergic conjunctivitis.

Often, antihistamines form a constituent of medications intended to treat cough and colds. In fact, the sedative action on the method of coughing and the anti-cholinergic actions that help to dry up the mucus secretions of antihistamines may prove to be useful.

Since the majority of antihistamine medicaments work to induce a depression on the brain, at times these drugs are also prescribed to promote sound sleep. This is done particularly when the uneasiness caused by itching is responsible for sleep disturbances. Nevertheless, latest antihistamine medications appear to have lesser sedative actions. As the depressive actions of antihistamines on the brain spread to the centres that regulate vomiting and nausea too, these medications are frequently used to treat these symptoms also.

At times, antihistamine medicaments are also prescribed to treat rash, fever and breathing problems that may happen as unfavourable reactions to blood transfusions as well as use of medicines to treat allergic reactions. As discussed above, antihistamines work to obstruct the exploits of histamines on a specific receptor called H1 receptor, which is present in different body tissues, especially those of the small blood vessels found inside the nose, skin and eyes. The action of antihistamines facilitates in putting off the widening or expansion of the blood vessels, thereby lessening the inflammation (swelling and redness).

Antihistamine medicaments circulate from the bloodstream to the brain, where it blocks the histamine resulting in general calms and depresses the various functioning of the brain, counting the coughing mechanisms and vomiting.

Very often, antihistamines result in sedation and may have an undesirable influence on coordination, resulting in ineptness. However, some of the latest antihistamines available in the market have very little sedative effect or may not have any such effect at all. Use of antihistamine medications may generally cause anti-cholinergic side effects, such as blurred vision, dry mouth and problems in urinating. The majority of such side effects actually lessen when the medications are continued. Moreover, the patients may get relief by adjusting their antihistamine medication doses or when they are treated with different medications.

It has been found that the older antihistamine medications may possibly have a distinct sedative action and, therefore, it is advisable that people taking these medications should stay away from activities that require alertness, such as driving a vehicle or operating machines, till they are sure about the action of the medication on their body. In addition, antihistamines also possess the aptitude to augment the sedative actions of alcohol as well as the medications taken to ease anxiety.

When taken in elevated doses or given to children, a number of antihistamine medications may trigger excitement. It has been found that people who have taken elevated doses of a number of the latest antihistamine drugs, for instance terfenadine, experienced an anomalous heartbeat. People who have taken macrolide antibiotics in conjunction with antihistamine medications, or individuals suffering from liver ailments, heart abnormalities that have been identified by means of an electrocardiogram or having electrolyte disturbances too have experienced abnormal heart rhythms when they took antihistamines. Therefore, it is advisable that people suffering from the above mentioned health conditions, glaucoma or problems related to the prostate ought to consult their physician prior to using antihistamines, as antihistamines interact with a variety of medications and this may actually result in the further deterioration of their condition.


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