What happens if you accidentally take two allergy pills in one day

Oral antihistamines, such as diphenhydramine (Benadryl) and cetirizine (Zyrtec), should never be taken together, as this can lead to dangerous complications.

Promotion disclosureinfoPromotion disclosureinfo

Save up to 72% on cetirizine with GoodRxDifferent pharmacies offer different prices for the same medication. GoodRx helps find the best price for you.

As the April showers pass and the May flowers come into full bloom, what often follows is a season filled with watery eyes, runny noses, and congestion. Seasonal allergies or hay fever affect an estimated 14% of adults in the United States. Even your pets can experience them!

Various allergy medications are available to be purchased over-the-counter (OTC) at the pharmacy. However, certain medications – especially those that belong to the same medication group – should never be taken together.

Read here to find out which allergy medications are safe to mix and which combinations can lead to serious problems.

What are the different types of allergy medications?

Allergies are triggered when your immune system overreacts to an allergen such as pollen, mold, or pet dander. Although these substances are generally harmless, your body may respond to them as though they’re dangerous and try to attack them. This results in the symptoms you may commonly feel: a stuffy nose, itchy eyes, and coughing.

Antihistamines

Histamines are chemicals made by your immune system to defend your body from potential threats. Your body releases these chemical signals when you encounter allergens. Antihistamines are a group of medications that relieve allergy symptoms caused by raised histamine levels. 

The most commonly taken antihistamines are those available as oral tablets or liquids. Older antihistamines, also known as first-generation antihistamines, can cause you to feel sleepier than newer antihistamines. Diphenhydramine (Benadryl) is a popular first-generation antihistamine and can cause other common side effects, including:

• Dry mouth 

• Dry eyes

• Constipation

• Blurry vision

• Dizziness

The newer, second- or third-generation antihistamines do not cause as much drowsiness as diphenhydramine. Medications like cetirizine (Zyrtec), loratadine (Claritin), desloratadine (Clarinex), fexofenadine (Allegra), and levocetirizine (Xyzal) also prevent allergy symptoms for a longer period of time than diphenhydramine. This is why many providers often recommend the newer antihistamines for seasonal allergies over older antihistamines.

Antihistamines also come in other forms. Olopatadine (Pataday) is an antihistamine eye drop used to treat itching and watery eyes. Antihistamines nasal sprays, such as olopatadine (Patanase) and azelastine (Astepro, Astelin), are used to treat nasal symptoms, including runny nose, itchy nose, and stuffiness.

Steroids

Steroids, also known as corticosteroids, treat allergy symptoms by reducing swelling caused by inflammation. Fluticasone propionate (Flonase), mometasone (Nasonex), Rhinocort Allergy, and Nasacort Allergy are common steroid nasal sprays used to relieve sneezing and itchy or runny noses. 

In very severe cases of allergies, oral steroids may be prescribed. Oral steroids include prednisone or prednisolone (Orapred, Pediapred). Steroid eye drops, such as loteprednol (Lotemax), are sometimes used for bad cases of eye allergies. Since these medications are powerful, they are usually only prescribed for a short period of time.

Decongestants

Allergens can cause the lining of your nose, as well as the blood vessels there, to swell. Decongestant medications help treat stuffy and congested noses by shrinking the swollen blood vessels. These medications can be taken by mouth or sprayed into the nose to treat allergy symptoms.

Pseudoephedrine (Sudafed) is a strong oral decongestant. Although it can be purchased without a prescription in most states, pseudoephedrine is stored behind the pharmacy counter, and there are limits to how much can be purchased at a time. Phenylephrine (Sudafed PE) is another common oral decongestant. Phenylephrine does not have the same restrictions as pseudoephedrine and can be found in the pharmacy aisles.

Decongestant nasal sprays, such as oxymetazoline (Afrin), are sprayed in the nose to lower swelling and relieve congestion. 

Decongestants are also sometimes combined with other allergy medications like antihistamines. You can usually tell if an allergy medication contains a decongestant if it has a “D” in the name, such as Allegra-D (fexofenadine/pseudoephedrine).

Montelukast

Montelukast (Singulair) is a leukotriene receptor antagonist. It works by blocking chemicals called leukotrienes that help create inflammation in your airways. Allergens trigger your body to produce high levels of leukotrienes, causing these airways to narrow and tighten and leading to congestion and stuffiness. 

However, due to the risk of serious behavioral and mood changes, such as suicidal thoughts or actions, the FDA recommends that montelukast only be used for severe cases of seasonal allergies. 

Is it safe to combine allergy medications together?

Some allergy medications, especially if they work differently in the body, can be safely taken together. For instance, someone taking an oral antihistamine, such as cetirizine, can also use antihistamine eye drops like ketotifen to treat itchy or watery eyes. However, keep in mind that oral antihistamines can cause dry eyes and worsen some allergy symptoms.

Nasal sprays, including steroids and decongestants, are sometimes used with oral antihistamines to treat allergy symptoms. These medications work in different ways to relieve symptoms, such as a runny nose or congestion. However, the American College of Allergy, Asthma, and Immunology recommends that a steroid nasal spray should first be used by itself to treat allergies since it is more effective than other medication classes. 

Which allergy medications should you never take together?

Although you can take some medications together to treat allergy symptoms, combining certain medications can be very dangerous. Different oral antihistamines such as diphenhydramine, cetirizine, loratadine, levocetirizine, desloratadine, and fexofenadine should never be taken together. Taking different oral antihistamines together can lead to an antihistamine overdose.

Signs of an overdose may include the following:

• Fast or racing heartbeat

• Dry mouth

• Agitation

• Behavioral changes

• Poor balance or coordination

In severe cases, an antihistamine overdose can result in serious complications including cardiac arrest, seizures, and even death.

If someone you know may be experiencing an overdose, call 911 immediately or use the Poison Control helpline at 1-800-222-1222.

Does combining allergy medications help or hurt?

In certain situations, your provider may prescribe both a medication that you take by mouth and a medication that you apply elsewhere, such as a nasal spray or eye drops. For severe allergies, your provider may recommend using a combination of a steroid and an antihistamine nasal spray.

Oral decongestants like pseudoephedrine are also sometimes taken with other allergy medications to relieve stuffiness and congestion. However, these medications may also cause side effects such as:

• Sneezing or dry nose

• High blood pressure

• Fast heartbeat

• Headache and dizziness

• Shakiness 

• Trouble sleeping

Some individuals, such as older adults or people with heart problems, may experience more side effects when taking many allergy medications. Make sure to discuss the risks and benefits of combining these treatments with your provider.

Is it a good idea to change the type of allergy medication you’re taking?

If you feel like your allergy medication has stopped working, you’re not alone. This is a relatively common problem. But changing medications may not be the right solution.

Although some people say that switching to a different antihistamine provides better relief, studies have not shown that antihistamines stop working when they are taken for a long time. For instance, research shows newer antihistamines like cetirizine provide the same amount of relief 180 days after first starting them. 

If you experience more allergy symptoms while taking your antihistamine, it may mean that your allergies are actually worsening. Therefore, you should speak with your provider to discuss potentially raising the dose of your antihistamine or adding a different medication, such as a nasal spray.

Are there ways to control allergy symptoms without medication?

An important part of managing allergies is avoiding allergens that may trigger symptoms. Common allergens include:

• Pollen

• Pet dander

• Mold

• Dust mites

• Cigarette smoke

A sinus flush, also known as nasal irrigation, may be helpful in clearing out potential allergens. It involves flushing out the nose with a salt solution using a device like a neti pot. However, it is very important to use distilled or sterile water to avoid harmful infections.

Having good air filtration within your home is also crucial in managing seasonal allergies. Studies suggest cleaning and replacing the air filters in your home’s heating, ventilation, air conditioning (HVAC) systems or using portable room air cleaners can lower the amount of allergens and improve allergy symptoms.

The bottom line

Many allergy medications are available OTC to treat seasonal allergies. Each works in a different way to relieve allergy symptoms. Some medications are taken by mouth while others are applied locally in the eyes or nose. The American College of Allergy, Asthma, and Immunology recommends most people try a steroid nasal spray first to treat allergies. 

Some people may need to combine different allergy medications to treat their allergy symptoms. However, you should never take different oral antihistamines such as cetirizine and loratadine together since doing so can result in dangerous complications. Make sure to discuss this with your provider to determine the best allergy medication to treat your symptoms.

Was this page helpful?

thumb_up_outlinedthumb_down_outlined

Subscribe and save.

By signing up, I agree to GoodRx's Terms and Privacy Policy, and to receive marketing messages from GoodRx.

Is it OK to take 2 allergy pills in 24 hours?

Will it hurt you if you take 2 allergy pills?

What happens if you take 2 Claritin by mistake?