Allergies occur when the body's immune system responds to a substance it considers an "invader." Substances that provoke the immune system into an allergic response are known as allergens. What might trigger a life-threatening allergic response in one person might cause absolutely no harm in another.
The physiological mechanism of allergic reactions is the same, however, in everyone.
Leukotriene inhibitors: Other substances released during an allergic reaction are leukotrienes, which can aggravate allergic conditions and asthma.
Leukotriene inhibitors are associated with unusual weakness, upset stomach, earache, dizziness, cough, headache, trouble sleeping.
Serious but unlikely side effects include flu-like symptoms.
The efficacy of antihistamines in the treatment of allergic rhinitis and urticaria is compared. They can be administered either once or twice a day.
In treating allergic rhinitis, the new second-generation antihistamines have multiple advantages including rapid onset of action, extended duration of action and efficacy for nearly all the symptoms that are produced by allergen sensitization. There is minimal potentiation for QTC prolongation, and they are safe and effective as first line therapies for seasonal allergic rhinitis.
Additional therapy may include H antagonists, antihistamine–decongestant combinations, tricyclic anti-depressants such as doxepin, beta-adrenergic agonists including albuterol and epinephrine for acute angioedema.
Corticosteroids may be required to treat significant exacerbations of chronic urticaria and/or to break a long-standing cycle of urticaria.
In addition to oral dosage forms, antihistamines come as creams, lotions, nasal sprays, and eye drops; the latter to relieve symptoms associated with allergic conjunctivitis.
Other types of allergy drugs include: Corticosteroids: These come as nasal sprays, topical creams and ointments, tablets, injectables and eye preparations. Mast cell stabilizers: These can help prevent allergic reactions from happening when taken regularly.
More severe, life-threatening allergy symptoms include swelling of the throat, wheezing and difficulty breathing.
Antihistamines used to treat allergy symptoms fall into two broad categories: sedating and non-sedating.
Newer antihistamines are said to be non-sedating, although some users may experience drowsiness even from these.