Many allergy sufferers, for example those with hay fever, deal with their allergies by taking medications during the pollen season. These so-called antihistamines block the action of the neurotransmitter histamine and reduce or prevent the onset of allergic symptoms. The cause of the allergic reaction, the response of the immune system to harmless substances, cannot be treated.
This overreaction is treated with immunotherapy (also called allergy vaccination or specific immunotherapy). Your child will be brought in contact with the specific allergen with an incrementally increased dose. Thus the immune system gets used to the substances and "learns" that they are harmless. Ideally, these substances are then blocked by different mechanisms and thus an allergic reaction avoided.