How Long Does It Take for Allergy Medicine to Work, and Should You Take It Every Day

Sneezing, itchy eyes, a runny nose: These are the telltale signs of spring for about 60 million people in the U.S. While seasonal allergies typically aren’t dangerous or life-threatening, they can make it more difficult to do normal activities and keep you inside when the weather is nice.

Because many allergy medications are available over the counter (OTC), most people can find a product to help ease or stop these irritating symptoms. But how long does it take for allergy medicine to work? And do you need to take them every day?

How long does it take for allergy medicine to work?

How long allergy medicine takes to work varies depending on the type of medication you’re using and the symptoms you’re treating. The fastest-acting allergy medications work within a few minutes. Slower-acting options may take 2 to 4 weeks to provide benefits. More details on fast- and slow-acting allergy medications next.

Both types of allergy medication have their time and place. Fast-working medications can be particularly helpful if you only get symptoms every now and then. But some of the slower-working options are among the most effective for allergy prevention.

Which medications provide fast relief, and how often should you take them?

If you’ve suddenly developed symptoms and are wondering how long it takes allergy medications to work, don’t worry. There are two groups of fast-acting allergy medications: decongestants and antihistamines. Decongestants may start working in 30 minutes or less. Most antihistamines take a few hours to fully kick in.

Decongestants (Sudafed, Afrin) 

Decongestants work the fastest to relieve certain allergy symptoms. They help relieve a stuffy nose and clear your sinuses. But they don’t help with sneezing, runny nose, or eye-related symptoms. They come as oral pills, oral liquids, and nasal sprays. Decongestant eye drops are also available, but they don’t help relieve nasal congestion. Oral decongestants typically start working in about 30 to 60 minutes. Nasal sprays can provide relief within 5 to 10 minutes.

Some well-known decongestants include:

• Sudafed (pseudoephedrine)
• Afrin (oxymetazoline)
• Neo-Synephrine (phenylephrine)

However, decongestants aren’t the right choice for everyone. You shouldn’t use them if you have heart problems like high blood pressure because they can raise your blood pressure. If you are pregnant or nursing, you should check with your prenatal care team before using any decongestant. They’re not safe for every stage of pregnancy.

Decongestants also don’t prevent allergy symptoms. So you should only use them when your stuffiness is at its worst. In fact, using Afrin, Neo-Synephrine, or other nasal spray decongestants too long and then stopping them can cause rebound congestion. This is when your congestion returns and is worse than before.

It’s best to take oral decongestants for no more than 7 days in a row and nasal decongestants for no more than 3 days in a row.

Good to know: Medications that contain pseudoephedrine are available without a prescription but are kept behind the pharmacy counter. Due to a risk of misuse, there are restrictions on how much you can buy per day and per month. And you have to show a federal or state-issued form of ID, such as a passport or driver’s license, to buy it.

Antihistamines (Zyrtec, Claritin, Allegra, Benadryl)

Another fast-acting allergy treatment is antihistamines. This group of medications helps calm down the body’s reaction to histamine — the chemical that likely causes allergy symptoms.

Oral antihistamines can treat multiple types of symptoms (like sneezing, itchy eyes, and post-nasal drip). They fully kick in within a few hours. Nasal spray antihistamines can start working in as little as 15 minutes. But they only treat nose-related symptoms. And antihistamine eye drops also work within a few minutes, but only treat eye symptoms.

Popular antihistamines include:

• Benadryl (diphenhydramine)
• Claritin (loratadine)
• Zyrtec (cetirizine)
• Allegra (fexofenadine)
• Astepro (azelastine) nasal spray
• Zaditor (ketotifen) eye drops

Antihistamines are a unique option for treating seasonal allergies. They work quickly to help get symptoms under control. But if taken every day, they can also help prevent symptoms from starting. Experts recommend those taking antihistamines for allergies to take them every day — instead of only when symptoms flare up — to maximize their benefits.

Which allergy medications take several days or weeks to work?

If you have decided to get ahead of your allergies, there are additional options to help prevent symptoms from starting. It’s important to note that these medications won’t provide fast relief, so it’s best to begin using them before allergy season begins.

Even if you didn’t start them beforehand, they can still be effective and are generally worth using. But you may want to consider taking a faster-acting treatment, such as an antihistamine, until the slower-acting medication starts working.

Intranasal corticosteroids (Flonase, Nasacort)

Nasal steroid sprays can keep your allergies at bay with very few side effects. Experts consider them to be a first-choice option for people with persistent allergy symptoms because they’re very effective for managing symptoms.

Well-known nasal steroid sprays include:

• Flonase (fluticasone propionate)
• Nasacort (triamcinolone)
• Rhinocort (budesonide)
• Nasonex (mometasone)

The biggest downside of these products is that they can take up to 2 weeks to work for some people. So it’s best to start using them before allergy season begins. Just be sure to watch out for side effects like nosebleeds while using these medications and contact a healthcare professional if this happens to you.

Singulair

Singulair (montelukast) is a prescription-only medication that works by blocking chemicals called leukotrienes, which play a role in both allergies and asthma. This once-daily oral tablet is generally less effective than other medications for preventing allergy symptoms. But it might be an option if you also have asthma, as it does work well for that condition.

You need to take Singulair daily for it to work properly. In studies, the medication took about 2 days to start preventing allergy symptoms. Full benefits are experienced after taking it for 2 weeks.

NasalCrom

NasalCrom (cromolyn sodium) belongs to a group of medications called mast cell stabilizers. It’s an OTC nasal spray that helps prevent certain cells in the body (mast cells) from releasing chemicals like histamine. It’s long been a recommended option for pregnant women with allergies because it has a lot of safety data available for this group.

One of the disadvantages of NasalCrom is that it can take up to 4 weeks to kick in. It’s also less effective than other allergy medications. Because of these drawbacks, it’s not typically a first choice for managing allergies.

When should you start taking medications to prevent seasonal allergies?

The short answer is: Start your preventative allergy medications about 2 to 4 weeks before you expect symptoms to start.

People with seasonal allergies usually only have symptoms during certain months of the year. So it’s typical for them to only use medications during those times. But for best results, start your preventative medication about 2 weeks before you would typically begin having symptoms (4 weeks prior if you’re using NasalCrom). This gives your body time to adjust to the medications and get the benefits of them.

If you have spring allergies, you might need to start your daily medications in early February, depending on where you live. People who have summer allergies should start their regimen in mid-May. If you have fall allergies, you might have to begin your routine in late July. And if you experience allergies during multiple seasons, it might be best to start in February and continue taking your medications daily until late fall.

Can you stop allergies immediately?

You can’t stop allergy symptoms immediately, but you can treat them pretty quickly. Fast-acting medications, like Sudafed and Zyrtec, start working with a single dose. And quick relief nasal sprays, like Afrin and Astepro, will work even faster than oral versions — often within 15 minutes.

Just remember that decongestants like Afrin and Sudafed shouldn’t be used for more than a few days at a time.

When is it safe to stop taking seasonal allergy medications?

There is no one-size-fits-all answer to this question. Watching for local pollen or mold counts to decline can help guide this decision. But everyone’s experience with seasonal allergies is different and can change from year to year.

Stopping too early can cause your symptoms to suddenly reappear and be difficult to get back under control.

It’s best to discuss this with a healthcare professional so you can come up with a plan on when to stop your allergy medication.

Can you take different types of allergy medication at the same time?

As a general rule, you can safely combine allergy medications that are in different classes. For instance, oral antihistamines and decongestants are often combined into a single tablet for convenience, like Claritin-D (loratadine / pseudoephedrine) and Allegra-D (fexofenadine / pseudoephedrine).

A good tip is to take an oral antihistamine while first starting a nasal steroid spray since the latter takes some time to start working. This tactic may be especially helpful if you didn’t start your daily regimen before allergy season began and need quick symptom relief. After about 2 weeks, you can try to stop the antihistamine and see if the nasal steroid is working well enough on its own.

In general, you should avoid taking two medications in the same class that you take the same way. For instance, taking two oral antihistamines can make side effects like drowsiness more likely. In rare cases, this combination can lead to serious side effects, including seizures, heart rhythm problems, and, in some cases, death. However, you could safely combine one oral antihistamine with an antihistamine nasal spray or eye drop.

If you’re considering adding a second allergy medication, it’s best to speak with your prescriber or pharmacist first. They can make sure the medications you’re taking won’t interact with each other.

When is it time to try a different allergy medication?

It’s not unusual for people to say their medication has “worn off” midway through allergy season. Many people believe it’s because they’ve developed a tolerance to their medications. But this is most likely not the case. It’s not common for people to develop a resistance to these medications.

It’s more likely one of the following is the reason your allergy medication has stopped working:

• There’s been a change in the type or amount of pollen or other allergen in the environment.
• Your body has developed a new allergy.
• Your stress level has recently changed.
• You’ve missed doses of preventative allergy medication(s).
• You're experiencing rebound congestion due to overuse of decongestant nasal sprays.

But if you know you’re using your medication appropriately, you’ve lowered your stress levels, and you’re taking steps to avoid being exposed to pollen and other allergens, then it might be time to change medications.

Sometimes, all you need to do is try another medication in the same class, such as switching from Claritin to Zyrtec. If that doesn’t seem to help, it’s time to see your primary care provider or an allergy specialist.