As the name suggests, antihistamines inhibit the effects of histamine (a mediator of allergy, a chemical compound present in the blood and most body tissues and released in nasal passages, eyes, lungs or skin during allergic reaction).
Antihistaminics ‘block’ the effects of the molecules of histamine that are released but do not change the way the body responds to an allergenic substance (birch, peanuts, cat allergen for example). Immunotherapy works at changing a person’s allergic response and encouraging a ‘normal’, non-allergic immune response. Immunotherapy consists in the repeated administration of small doses of pollen or other allergen substances responsible for an allergic response in patients with respiratory allergies. While antihistaminics only mask or hide the symptoms of respiratory or seasonal allergies, immunotherapy induces tolerance to the offending allergen in an effort to change the course of the allergic disease. For most people this controls the symptoms within a matter of a few weeks. Ultimately, remanence, or the persistence of the protective effect is achieved. Although immunotherapy cannot yet promise to cure every type of allergy in every person, it nonetheless represents quite a powerful alternative to reduce the risk of developing new allergies or asthma while carrying efficient relief of allergy symptoms. Although traditionally administered through shots or injections (subcutaneous), which have proved to be very effective in vespid (bee and wasp) allergic patients, more recently it is sublingual immunotherapy either through the daily administration of allergen drops or tablets under the tongue (sublingual), that has recently gained popularity in the treatment of respiratory allergies.