Eli5: How do antihistamines work and what is the difference between first generation and second?

Question

Eli5: How do antihistamines work and what is the difference between first generation and second?

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Answer 1

Antihistamine, like the name suggests, is a drug that blocks the effects of histamines. First gen blocks histamines and muscarinic receptors, second gen just blocks histamines. Second gen also doesn’t make you drowsy