Allergy symptoms. Allergy medicine. Allergy

Allergy is a condition of increased sensitivity of a living organism to a certain type of compound (allergens), which is developed on the second encounter with this compound. Physiological mechanism of allergy development consists in appearance of antibodies in the organism, which leads to decrease or increase in its sensitivity.  Allergic reaction is a type of hyper reaction to a certain factor of the environment.

But what are allergy symptoms and how do they differ from the kind of allergy we have?

The most widespread type of allergic reaction is respiratory allergy. Such a reaction can be caused by vapors, small dust particles, perfume, pollen, which can be found in the air. Respiratory allergy manifests in the following allergy symptoms, which are commonly mistaken for a common cold, like: sneezing, runny nose, coughing, inching in the nasal area. Allergic background can be traced in an illness called bronchial asthma. Also the allergens that can be found in the air can cause lacrimation, eye irritation, itching. The observed symptoms like the one mentioned before can often be mistaken for a flu and treated in the same way with anti-flu medicine, but an allergy can't be cured with their use. Also an allergy manifests without hypothermia, the sneezing is frequent and hard to cure.

According to statistics the second type of allergic reactions which are frequently observed are contact allergies or dermatosis. They appear from the use of cosmetics, during the work with pharmaceutical products, latex, household chemical goods and many other compounds (defined by the peculiarities of the organism). Symptoms of allergic dermatosis consist in - skin rashes, itching, swelling, appearance of blisters, peeling.

The most dangerous type of allergy still has still not been mentioned - allergy to food products and drugs. The allergen is delivered into the organism through gastro-intestinal tract. The allergy can manifest in such allergic symptoms like: nausea, vomiting, tongue and larynx swelling, diarrhea, stomach pain. Subsequently allergic reaction can spread to the skin and cause allergic dermatitis.

The most severe type of allergic reaction is anaphylactic shock, which is mostly developed due to a reaction to drugs or insect bites. The symptoms of anaphylactic shock should be known by everyone: loss of consciousness, convulsions, difficulty breathing, rash all other the body, involuntary act of defecation and urination. If a possibility of anaphylactic shock is suspected, you should call your local  health care provider and urgently go to the hospital.

How fast an allergic reaction can manifest? The speed of manifesting of allergic symptoms differs from the path of development. Four types of allergic reactions can be defined. They differ by the type of cells which produce the immune response. For example, an anaphylactic shock can manifest itself within 1 minute to few hours after the contact with allergens. Skin dermatosis and respiratory allergies can start within 15-20 minutes after breathing or skin contact with the allergic compound. Drug and food allergies usually manifest within a 24 hour period, and in the end the slow type of reactions (which are possible due to severe infections or organ transplant) occur within 1-3 day period.

Allergy medicine

In most cases allergy is treated by anti allergy medicines. Anti-allergic medicines are preparations used for prophylaxis and treatment of allergic diseases. For the last 20 years anti-allergic medicines became in great demand on the pharmaceutical market. This situation is determined by a hasty growth of patients with allergic diseases. High frequency of these allergic conditions is related to appearance of a range xenobeotic substances(drugs, chemical industry, food supplements) and increasing the sensitivity of the human organism to these compounds.

Up-to-date pharmaceutical market is able to offer a lot of allergy medicines. All of them can be divided into 2 main group:
1.Blockers of allergy mediators(histamine, seratononin, bradykinin, leukotriene)
2.Mast cell membrane's stabilizes

Blockers of H1-histamine receptors are the most popular among all anti-allergic drugs. H1-histamine blockers are available under the brand names Claritin(loratadine), Zyrtec(cetirizine), Aerius(desloratadine). These medicines belongs to 2nd generation of antihistamine blockers, meaning that they do not cause some side effects associated with first generation of antihistamines. 
The action mechanism of Zyrtec, Claritin and Aerius arises from the selective inhibiting of H1-histamine receptors. Histamine is an allergic mediator that is released from the mast and basophilic cells when some allergens (foreign substances) enters the blood circulation.
When histamine is released, it binds to specific H1 receptors causing some physiological changes such as dilatation of the  capillaries, lowering of the blood pressure, increasing of capillary permeability. All of these results in sneezing, nasal congestion, inflammation of the mucous lining of the skin, nose, runny nose, watery and itchy eyes, runny nose).
By blocking histamine receptors, Zyrtec, Claritin and Clarinex relieves allergy symptoms. These antihistamine agents are prescribed in the following conditions:

•         Seasonal and all year round allergic rhinitis manifested in sneezing, itching and rhinorrhea
•         Allergic conjunctivitis.
•         Acute and chronic hives
•         Quincke's disease and other skin allergic diseases 
•         Allergic reaction associated with insect bites
• In spite of similar indicates, these antihistamine agents possess different pharmacotherapeutic, pharmacokinetic features.

Let's begin with Zyrtec. Zyrtec (cetirizine) is available in 2 pharmaceutical phorms(coated tablets and drops)
After intake, Zyrtec is quickly absorbed into the blood circulation, C max is achieved in 1 hour. Concomitant food intake may increase drug's absorption till 2 hours. Cetirizine is metabolized in the liver without interacting with cytochrome P450. It means that Zyrtec (cetirizine) can successfully be used in conjunction with . Cetirizine is eliminated in unchanged form with urine and 10% with motions.  Zyrtec can be indicated in children over 6 month.
Zyrtec should not be used in pregnancy, breastfeeding. Patient with chronic kidney failure should use the medications with caution.
Zyrtec is well tolerated. In rare cases some patients with individual intolerance may experience dizziness and dyspepsia. 
Another antihistamine drug is Claritin (Loratadin). Claritin is quickly absorbed from the digestive system. Cmax is achieved in 1.3 hours. Loratadin is metabolized in the liver through the enzymes  CYP450 and CYP2D6. Thus, Claritin should not be taken in conjunction with cytochrome inhibitors(ketaconazole, erythromycin, cimetidine). Claritin is contraindicated in pregnancy, breastfeeding and liver diseases. Claritin can be used in children only over 2 years of age.
Desloratadine (active ingredient of Clarinex) is an active metabolite of loratadine. Desloratadine is metabolized in the liver (without interacting with cytochrome P450) and is eliminated out of the body within 28 hours. This allows desloratadine to exerts prolonged anti-allergic effects.
Desloratadine should not be used in pregnancy and breastfeeding. Children less than 12 years of age should take Aerius with caution.
The affinity of desloratadine to H1 receptors and therapeutic activity is much higher that in loratadine. This makes possible to decrease dosage of desloratadine to 5mg. In addition, desloratadine exerts moderate anti-inflammatory action due to the inhibiting the inflammatory mediators(IL, TNF-a, GM-CSF).
Summarizing the above information we would to point on some important facts:

•   Zyrtec is more convenient anti-allergic preparation in pediatric use.
•   Claritin can successfully be used in people with healthy liver. 
•   Clarinex is a preparation of choice in children over 12 years of age and in adults. Unique anti-allergic properties make Aerius indispensable in allergy treatment.