2933.99.26.00 - Antihistamines

This HTS category, 2933.99.26.00, specifically classifies antihistamines. These are chemical compounds characterized by their heterocyclic structures containing nitrogen heteroatoms, falling under the broader classification of organic chemicals. Antihistamines function by blocking the action of histamine, a substance released by the body during allergic reactions, thereby alleviating symptoms such as itching, sneezing, runny nose, and hives.

This category is distinct from its sibling categories such as "Anti-infective agents," "Cardiovascular drugs," and "Drugs primarily affecting the central nervous system" by its specific pharmacological action. While all may fall under the general heading of "Drugs," antihistamines are uniquely defined by their role in managing histamine-mediated responses. The "Other" designation at the preceding levels indicates that this classification applies to antihistamines not otherwise specified in more granular subcategories.

As this is a leaf node within the HTS structure, there are no further subcategories for antihistamines. Therefore, classification at this level relies on the definitive identification of the substance as an antihistamine by its chemical structure and intended pharmaceutical use, as confirmed by relevant regulatory or scientific documentation.