What is allergy tablets do?

Allergy tablets. Most allergy tablets are medications that fall into the category of antihistamines that block the effect of histamine. This treats symptoms such as sneezing, itching, runny nose, etc. Sometimes antihistamines are combined with decongestants to help with stuffy nose. Studies are evaluating "allergy tablets" that may work similar to allergy shots where the tablet contains the pollen, etc.
Allergy pills. Most otc allergy tablets block h1 histamines and are known as antihistamines. The prescription allergy tablets like singulair (montelukast) and Accolate are leukotriene receptor antagonists that block a receptor also involved in the allergy cascade.