Antihistamines are medications that treat allergy symptoms, such as a runny nose, hay fever, itchy eyes, and sneezing.
They work by blocking the effects of histamine, a chemical released by the body during allergic reactions. Common over-the-counter (OTC) antihistamine brands include Benadryl, Zyrtec, Claritin, and Xyzal.
Antihistamines aren’t as addictive as other CNS drugs like opioids, morphine, heroin, and fentanyl, but they have a high potential for dependency.
Those who take antihistamines regularly may develop a psychological dependence on the drug, with many taking the drug as a way to cope with stress, calm anxiety, or induce sleep.
Long-term use of antihistamines can result in negative health effects, including memory problems, cognitive impairment, seizures, and increased heart rate.
This article discusses antihistamine withdrawal symptoms, how people misuse antihistamines, and how to safely take antihistamines to avoid dependency.
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What Are the Withdrawal Symptoms of Antihistamine Use?
While generally safe when used as directed, those who take antihistamines regularly over long periods or at high doses may experience withdrawal symptoms if they suddenly stop using the drug.
These symptoms can range from physical discomfort to psychological effects, and may include:
- Nausea
- Vomiting
- Anxiety
- Diarrhea
- Irritability
- Sweating
- Headaches
- Muscle stiffness
- Confusion
- Drowsiness
- Dizziness
- Difficulty breathing
- Severe itching
- Blurred vision
- Dry mouth
- Upset stomach
The withdrawal symptoms of antihistamine medications aren’t as potent as those associated with substances like opioids, benzodiazepines, or alcohol, but they can still be uncomfortable and disruptive.
Many of the symptoms are psychological rather than physical, which is why antihistamine withdrawal isn’t typically classified as ‘severe’ in most medical settings.
Withdrawal usually starts 48 to 96 hours after the last dose.
How Long Does Antihistamine Withdrawal Last?
The duration of antihistamine withdrawal depends on the type of antihistamine used, how long it was taken, the dosage, and individual factors like metabolism and overall health.
Generally, though, antihistamine withdrawal is relatively short-lived.
Physical symptoms like nausea, restlessness, anxiety, and irritability may last anywhere between 3 and 7 days, while psychological symptoms can last up to 6 to 8 weeks.
Individuals who have been taking antihistamines for a long time and quit cold turkey often experience a more intense and uncomfortable withdrawal compared to those who taper off gradually.
What Are Rebound Allergy Symptoms?
Rebound allergy symptoms refer to the return and sometimes worsening of allergy symptoms after stopping antihistamine, particularly following long-term or frequent use.
These symptoms usually appear shortly after stopping antihistamines and may feel more intense than the original allergic reaction the medication was intended to treat.
Common rebound allergy symptoms include:
- Sneezing fits
- Runny or congested nose
- Itchy or watery eyes
- Head pressure or sinus discomfort
- Throat irritation
Why Do Rebound Allergy Symptoms Occur?
Antihistamines work by blocking histamine, a natural chemical the body releases during allergic reactions.
When you take antihistamines regularly, your body may try to compensate by increasing histamine activity or sensitivity.
So when you abruptly stop taking antihistamines, especially after a period of using them regularly, your system becomes temporarily overreactive to allergens. This can result in rebound allergy symptoms.
People who experience rebound allergy often go back to using antihistamines to relieve the symptoms, creating a cycle of dependence. Over time, this pattern makes it harder to stop the medication altogether.
When you experience rebound allergy symptoms, the best way to manage them is to use alternative treatments like nasal corticosteroids, saline sprays, and air purifiers.
You’ll also want to avoid known allergens for a day or two until the symptoms disappear or become tolerable. For example, if you’re allergic to pet dander, you may want to avoid touching or going near your pet, or stay at a location free of pet dander for several days.
If the symptoms don’t go away within 3 to 5 days, consult with a healthcare provider for further advice.
How Do I Know If It’s Rebound Allergy and Not Something Else?
If you’ve recently stopped taking antihistamines, you may be wondering whether your symptoms are due to rebound allergy or a different condition. Here are some signs that point to the former:
- Symptoms began shortly after stopping antihistamines or nasal sprays (within a day or a few days).
- Symptoms feel worse than before you started the medication.
- Symptoms appear even when your environment or lifestyle hasn’t changed. You’re not around new allergens, pets, dust, or pollen.
If your symptoms include fever, body aches, sore throat, or thick yellow/green mucus, it’s likely that you’re experiencing an infection rather than antihistamine withdrawal or rebound allergy symptoms. Usually, these symptoms go away on their own within 7 to 10 days with proper rest and medication.
How Do People Misuse Antihistamines?
According to a study published in the Journal of Child and Adolescent Psychopharmacology, individuals who use antihistamines recreationally do so for their hallucinogenic effects.
The typical dose of antihistamines generally ranges from 24 mg to 300 mg per day, depending on the drug type. People who seek the hallucinogenic effects of antihistamines take 300 to 700 mg per day, and those who have developed antihistamine dependence use over 1,000 mg per day over periods of months or years.
Many people also take antihistamines with other substances to intensify sedation, like alcohol, opioids, or benzodiazepines.
Is an Antihistamine Overdose Deadly?
Yes, there have been a number of reported deaths due to antihistamine toxicity. Taking more than the prescribed amount can pose serious health risks and can lead to life-threatening complications. These side effects may include:
- Hallucinations
- Agitation
- Delirium
- Rapid or irregular heartbeat (tachycardia or arrhythmia)
- High blood pressure, or in some cases, dangerously low blood pressure
- Cardiac arrest
- Slowed or stopped breathing
- Severe agitation or psychosis
- Loss of balance
From 2019 to 2020, antihistamines were detected in about 15% of all overdose deaths in the United States, according to the CDC. Around 3.6% of these deaths involve antihistamines as a contributing cause.
Deaths caused exclusively by antihistamines without other drugs involved were very rare, accounting for fewer than 0.1% of overdose deaths (90 cases) during this period.
Diphenhydramine, a first-generation H1 antihistamine found in over-the-counter medications like Benadryl, is the most frequently abused antihistamine. This is largely due to its widespread availability, low cost, and psychoactive properties at high doses.
There’s currently no specific antidote for diphenhydramine overdose, and treatment involves supportive care and various interventions depending on severity.
How to Safely Use Antihistamines
The best way to safely use antihistamines is to take them as prescribed by a medical professional.
If you’re taking it to treat temporary symptoms like allergies, colds, or occasional sleep problems, use the lowest effective dose for the shortest necessary duration (3 to 5 days maximum).
If you’re taking them for long-term conditions such as chronic allergies, skin conditions (like hives), or anxiety-related issues, your use should be supervised by a healthcare provider.
In these cases, second-generation antihistamines (like loratadine, cetirizine, or fexofenadine) are generally preferred because they are non-sedating, better tolerated, and safer for extended use.
First-generation antihistamines like diphenhydramine or chlorpheniramine aren’t recommended for long-term use due to the risk of cognitive impairment and psychological dependence.
Here’s a guide to the recommended dosage of common antihistamines:
| Antihistamine Type | Adults | Max daily dose |
| Diphenhydramine (Benadryl) | 25 to 50 mg every 4 to 6 hours | 300 mg |
| Chlorpheniramine | 4 mg every 4 to 6 hours | 24 mg |
| Hydroxyzine (Vistaril, Atarax) | 25 to 100 mg, 3 to 4 times daily | Dosed by weight; must be prescribed |
| Loratadine (Claritin) | 10 mg once daily | 10 mg |
| Cetirizine (Zyrtec) | 10 mg once daily | 10 mg |
| Fexofenadine (Allegra) | 60 mg twice daily or 180 mg once daily | 180 mg |
FAQs
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Conclusion
While antihistamines are effective for managing allergies and related conditions, long-term or excessive use can lead to dependence, withdrawal symptoms, and even serious health risks. Recognizing the signs of misuse—whether it’s rebound allergy symptoms, withdrawal discomfort, or using antihistamines for purposes other than allergies—is the first step toward breaking the cycle.
If you find yourself relying on antihistamines beyond their intended use, talk with a healthcare professional about safer alternatives and strategies for tapering off. With the right guidance, you can manage your allergies effectively without compromising your overall health and well-being.
