A look at what's causing problems in the nose, lungs, skin, and eyes gives us a good idea about why antihistamines are a common treatment for allergies. These medications work by binding to histamine receptors, blocking histamine from doing so and otherwise starting the cascade of allergy symptoms. "The antihistamines work the day you use them," says White. "They don't do anything long-term in terms of cutting down on the allergic reaction." Antihistamines are very effective but are only half of the one-two punch many people with allergies use.