Does allergy medicine expire? Yes, but it may still be effective

• Allergy medicine expires, but it may still be effective for up to two or more years after the expiration date.
• Liquid allergy medicine, such as nasal sprays, tend to expire earlier than antihistamine tablets, and they will lose effectiveness more quickly after expiring.
• This article was medically reviewed by Omid Mehdizadeh, MD, otolaryngologist and laryngologist at the Pacific Neuroscience Institute's Pacific Eye, Ear & Skull Base Center at Providence Saint John's Health Center in Santa Monica, CA.
• Visit Insider's Health Reference library for more advice.

Yes, allergy medicine will expire eventually. However, depending on the type of medication, you may still get some relief after the expiration date has passed.

Over-the-counter and prescription antihistamine tablets tend to stay effective longer than liquid medicines, such as corticosteroid nasal sprays.

Here's what you need to know about when the different types of allergy medicine expire and how long after they may still be effective to take.

When do antihistamines expire?

Antihistamines, one of the main types of allergy medicine, can be safe to use after the expiration date.

For over-the-counter medicines like Claritin and Zyrtec, the listed expiration dates are typically around two and a half years after manufacturing. Expiration dates for prescription antihistamines are around one year, according to New Jersey-based pharmacist Kristin Frank.

OTC and prescription tablets are similar in makeup, and therefore can last the same amount of time. But prescriptions, by law, cannot have longer than one-year expiration dates.

All allergy medicines are regulated by the FDA, which takes a strict, no-leeway stance on expired medicine for utmost safety and effectiveness. But a 2012 study in the JAMA Internal Medicine Journal found that expired medicines, including antihistamines, can remain effective for decades.

The researchers studied the active ingredients in a set of decades-old drugs. Twelve of the 14 medications tested, including the antihistamine, retained full potency for at least 28 years. So why do antihistamines have a one-to-two-year shelf life?

According to Frank, manufacturers suggest expiration dates based on how long the active ingredients can stay potent. Manufacturers submit this research, which factors in storage variables like heat and humidity, when applying for drug approval to the FDA.

By the time drugs reach consumers, they could have been stored in conditions causing active ingredients to deteriorate, such as extreme temperatures, according to the FDA.

"The active part of the drug, the part that creates the body's response, would slowly break down over time and make it ineffective," says Frank. "Taking expired medicine then becomes like taking a placebo. It probably won't help you."

That's why after the expiration date, the manufacturer won't guarantee efficacy. But overall, antihistamines can still be effective for years after their expiration date. Just keep in mind that once you get two or three years past expiration, there's a higher chance that it's no longer effective.

Liquid allergy medicine and nasal sprays expire earlier

While most antihistamines are tablets, corticosteroids are in liquid form, and used to treat symptoms like itchy noses, sneezing, and nasal congestion.

Corticosteroid nasal sprays can be over-the-counter, like Flonase, or by prescription, like Nasonex. They contain preservatives to keep the liquids fresh longer.

Prescription liquid medicine expiration dates are no longer than one year, by law, although sometimes the manufacturer sets the shelf life at six months or earlier. Expiration dates for over-the-counter liquids are usually around two years.

And liquid allergy medicines shouldn't be stretched as far beyond their expiration dates as tablets, Frank says.

Frank says nasal sprays, as well as liquid forms of antihistamines, can last for one year beyond the bottle's expiration date. After that, the efficacy dwindles. "Like tablets, these drugs won't be unsafe when expired," Frank says. "They'll just become ineffective."

To extend the potency of liquid drugs like nasal sprays, Frank suggests keeping them at room temperature. "Storing in a room that's too warm, in sunlight, or colder like a refrigerator would make it go bad faster," she says.

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• How to determine which allergy medicine works best for you
• All the ways you can control your allergies, from air filters to saltwater rinses
• When is allergy season? Symptoms and treatment for seasonal allergies
• Hay fever is an allergic reaction that causes sneezing and a runny nose
• Is it a cold or allergies? How to categorize your symptoms and treat them appropriately