There are two main types of antihistamines first-generation and second-generation. First-generation antihistamines, such as diphenhydramine and chlorpheniramine, tend to have sedative effects, which can be advantageous for anxious horses but may not be suitable for those requiring full alertness. On the other hand, second-generation antihistamines, like cetirizine, typically lack sedative properties, making them a better option for horses that need to maintain their activity levels.
