Despite affecting some 50 million Americans, allergies aren’t super well understood. The sparks that ignite your immune system can range from sunlight to onions, and symptoms of an attack are just as varied. For that reason, we’re spending several weeks writing about allergies—what they are, how they manifest, and how we can find relief. This is PopSci’sAllergic Reaction.
We may not know much about allergies, but gosh darn it do we have some great drugs for them. In the United States, the allergy aisle in a typical pharmacy is a veritable Baskin Robbins of drug options. Nasal sprays. 24-hour non-drowsy pills. Sleep-inducing, decongesting, grape-flavored serums. We’ve got it all.
But how do you choose? Ask your friends, and you’ll probably get five different recommendations on which is absolutely the best. And unfortunately for you, they’re all correct.
“Figuring out which medications are right for you is like trying to navigate a complex roadmap for a long road trip,” says Sarena Sawlani, Medical Director at Chicago Allergy and Asthma. “There usually isn’t a ‘one size fits all’ approach.” She explains that different medications—and combinations of them—will suit individuals differently, and the results depend a lot on the situation. Is the user in an area with a new potential allergen? Do they take other drugs that alter their immune system?
Even if the context seems pretty neutral, Sawlani says that “we are all wired a bit differently, and so a personalized approach to finding the right medications for each individual is important. The medications may work through the same mechanisms, but we all may respond differently depending on what’s causing the symptoms and how our bodies handle them.”
Different pills work for different people… we’re just not sure why
Antihistamines aren’t all created equal—but it’s pretty close. The pills labeled as such in the allergy aisle all work on the same basic principle:
Allergy symptoms are caused by your body reacting to irritants like pollen or pet dander and releasing large quantities of a chemical called histamine. Histamine expands your blood vessels and increases mucus production, among other things, by attaching to receptors on the cells in your nose and sinuses. Antihistamines work because they look kind of like histamine, and can, therefore, bind to histamine receptors—except better. They’re designed to have a very high affinity for histamine receptors, such that they compete with histamine for the sites. The difference is that antihistamines don’t activate the receptor, and thus block the effects.
The only real differences between pills like Allegra (fexofenadine), Zyrtec (cetirizine), and Claritin (loratadine) are how the body metabolizes them. Loratadine gets processed a lot by your liver, whereas cetirizine and fexofenadine don’t as much. This shouldn’t have an effect on how well they bind to histamine receptors, but depending on your personal metabolism and liver, it may change the side effects. We don’t know much about what these metabolites might affect or how exactly they alter the overall function of the drug. We just know that some people won’t react the same way to the same drug, so if the metabolites of loratadine don’t sit well with you, another brand may be better.
Some of the antihistamines also work a bit better on rashes and other skin symptoms. Cetirizine and fexofenadine tend to accumulate more in your skin tissue, so they have a slightly higher impact on the histamine receptors there than loratadine does. But again—your mileage may vary.
But nasal sprays definitely seem to work better
The one thing that holds clear across all the drug options is that corticosteroids seem to work the best. Corticosteroids are the active ingredient in those nasal sprays you see, and though they take longer to become fully effective, they control symptoms better in the long-term. That’s because they don’t just prevent histamine from binding to its receptor—they prevent inflammatory cells from starting to react even before histamines can enter the picture.
This system works best after the steroids have built up a bit in your system and have had longer to modulate your immune response, so it’s best to start taking them a few weeks before allergy season begins.
Pro tip: try combining an antihistamine and a corticosteroid. Since they work through slightly different mechanisms, the combination could help get rid of those last few pesky symptoms. Though as Sawlani noted, different combinations will work better for some people and not for others, so expect some trial and error.