Side effects of short-term use of antihistamines are typically mild and cease when you decrease the dose or stop taking them. Although generally safe on an as-needed basis, taking antihistamines daily may bring about lethargy, dry mouth, and lightheadedness. Taking antihistamines over many years could increase the risk of high blood pressure, glaucoma, and certain types of cancers.

Understanding Antihistamines

Antihistamines are a class of medications used to treat allergy symptoms most commonly. They work by blocking the effects of histamine, a chemical released in response to an allergen that causes inflammation and other symptoms such as sneezing, runny nose, and itchy eyes. There are two generations of antihistamines available on the market: first-generation drugs–sedating–and second-generation drugs–non-sedating. They are typically determined by their ability to pass the blood-brain barrier at the approved doses. 

First-generation antihistamines, such as diphenhydramine (Benadryl), chlorpheniramine (ChlorTrimeton), clemastine fumarate (Tavist), and brompheniramine maleate (Dimetane) have been available since the 1950s. According to our medical reviewer, Maheed Javed, “sedating antihistamines can induce a variety of short-term side effects, including urine retention, constipation, dry mouth, increased hunger, and worsening narrow-angle glaucoma via acting on cholinergic receptors. However, the majority of adverse effects are minor and resolve when the medicine is discontinued or the dose is lowered.” Due to their sedative effects, first-generation antihistamines should be taken with caution during activities requiring alertness.

Second-generation antihistamines were developed more recently and include loratadine (Claritin), cetirizine hydrochloride (Zyrtec), desloratadine (Clarinex), levocetirizine, and fexofenadine hydrochloride (Allegra) and are generally used long-term to treat allergies such as eczema, sinusitis, or hay fever. The newer antihistamines are less likely to cause drowsiness because they don’t cross into the brain as easily as the first-generation drugs; however, some people may still become sleepy when taking them.

Beyond allergies, antihistamines are commonly used for:

• Seasonal allergies (hay fever): to alleviate symptoms like sneezing, itching, and nasal congestion caused by pollen from trees, grass, and weeds.
• Perennial allergies: for symptoms due to year-round exposure to allergens like dust mites, pet dander, or mold.
• Food allergies: to relieve mild symptoms, although they are not suitable for preventing serious reactions like anaphylaxis.
• Insect bites and stings: to reduce itching and swelling.
• Hives and other skin reactions: to decrease itching and appearance of rashes.
• Some antihistamines can also be used for other purposes, such as aiding sleep (due to their sedative effects) or relieving motion sickness.

The duration for which people use antihistamines can vary widely depending on the type of allergy and the severity of symptoms. In the short-term, antihistamines are typically used for acute allergic reactions, such as those caused by a specific allergen exposure (e.g., pet dander during a visit to a friend’s house with pets) and may be used for just a few days. They can also be used seasonally for seasonal allergies, such as hay fever during pollen season. In this case, antihistamines might be used daily throughout the season, which can last several weeks to months depending on the pollen counts in the area. Regarding chronic use, for perennial allergies for instance, which are year-round, some individuals might take antihistamines on a long-term basis.

Overuse Can Lead to Ineffectiveness

Overuse of antihistamines can lead to tolerance or lack of clinical effects. Tolerance occurs when the body develops a resistance to certain allergens. Signs that indicate you have developed tolerance include no longer experiencing relief from symptoms after taking your usual dose or having difficulty sleeping without using higher amounts each night.

It’s important to take only the dose of antihistamines necessary for symptom management, as larger doses are more likely to generate a tolerance than lower ones. While newer generations of drugs may be more resilient against tolerance, this is not always the case and depends on factors such as the severity of allergies or health conditions. 

When it comes to first and second generation antihistamines, Javed described how tolerance is a particular issue with first generation drugs, especially when “used for more than 4-5 days in a row.” Fortunately, tolerance was found not to be an issue with second generation antihistamines, with “no major negative effects recorded.”

How Long is Too Long to Take Antihistamines?

There is not a direct answer to this question. Although non-sedating, second-generation, antihistamines are generally considered safe for long-term daily use, you should discuss your usage with a healthcare professional if you are planning on taking them for an extended period of time. As Javed mentions, “new studies highlight the importance of prudent prescription methods, particularly in vulnerable groups”. This is particularly important if you have any underlying medical conditions like heart disease or high blood pressure, or if you are taking other medications that could potentially interact with antihistamines.

It’s also worth noting that taking antihistamines for more than three months may warrant a consultation with your doctor. This is especially necessary if your symptoms persist even after taking the medication, or if you experience severe side effects such as seizures or a severe skin rash.

Potential Side Effects of Antihistamines from Long-Term Use

While they can be effective in relieving symptoms such as sneezing, runny nose, and itchy eyes, long-term use of antihistamines may have some serious side effects. Javed further mentioned the significant relationship between antihistamines and side effects such as hypertension and glaucoma.

Moreover, when it comes to second-generation antihistamines, excessive or prolonged usage may bring about potential adverse effects, such as liver damage. Excessive use can also increase other health risks, including increased blood pressure levels. Being aware of how antihistamines relate to not only cognitive consequences, including dementia and mood disorders, but also physical consequences, such as weight gain, is important in understanding how to properly use them.

Weight Gain and Antihistamines

Antihistamines that have a sedative effect, such as first-generation antihistamines, may cause weight gain due to increased appetite and decreased physical activity. However, second-generation antihistamines are less likely to cause weight gain as they do not have a sedative effect. While weight gain is a potential side effect of antihistamines, it is not a common occurrence and it is important to discuss any concerns with your healthcare provider. In some cases, weight gain may be caused by underlying medical conditions that require additional treatment.

Remember, antihistamines work by blocking the neurotransmitter histamine, as the name implies. Histamine is important as it regulates many processes in the body, including appetite. Histamine typically reduces appetite, but if antihistamines block the effects of histamine, it may cause hunger and lead to weight gain. While the exact mechanism by which antihistamines cause weight gain is not fully understood, it is believed that they may stimulate the brain’s reward center, leading to increased food intake and cravings.

Some commonly used antihistamines that may cause weight gain include diphenhydramine (Benadryl), cetirizine (Zyrtec), and loratadine (Claritin). These medications can cause increased appetite and cravings, leading to overeating and weight gain.

While weight gain can be a concerning side effect of antihistamines, there are ways to mitigate this risk. Maintaining a healthy diet rich in whole foods and lean protein and exercising regularly can help prevent weight gain while taking antihistamines. Additionally, talking to your healthcare provider about any concerns regarding the potential side effects of antihistamines can help identify the best treatment options for managing allergy symptoms while minimizing undesirable side effects.

Antihistamines and Dementia

Research suggests that long-term use of certain antihistamines, such as diphenhydramine, may increase the risk of developing dementia. Diphenhydramine-sold commercially as Benadryl-is a first-generation antihistamine that is known for its sedative effects and is commonly found in over-the-counter sleep aids and allergy medications. A study published in the Journal of the American Medical Association found that adults who regularly took diphenhydramine or other first-generation antihistamines for at least three years had a 63% increased risk of developing dementia compared to those who did not regularly take these medications. The risk was even higher for those who took higher dosages of the medication. Moreover, another study according to the Cleveland Clinic that researched Diphenhydramine found that it blocks the effects of the neurotransmitter acetylcholine which is vital for memory and learning. Diphenhydramine increased the risk of dementia by 54 percent in one study of 3,000 patients followed for seven years.

Antihistamines and Depression

Studies have suggested that certain antihistamines may be linked to mood disorders. Specifically, long-term use of certain types of antihistamines are thought to possibly increase the risk of depression symptoms. This is especially true for first-generation antihistamines, such as diphenhydramine, which have been linked to depressive symptoms in elderly patients. However, the connection between antihistamines and depression is still under investigation and requires more research for a better understanding of the relationship.

One study published in The Primary Care Companion for CNS Disorders found a potential association between the use of cetirizine, a second-generation non-sedating antihistamine, and increased depressive symptoms in some patients. Similarly, hydroxyzine, a first-generation sedating antihistamine, has been linked to an increased risk of depression in elderly patients.

It should be noted that these studies have limitations, such as a small sample size and a correlational design that cannot prove causation. More comprehensive studies are needed to better understand the connection between mood disorders and antihistamines.

Despite the potential risks associated with long-term antihistamine use and its potential link to mood disorders like depression, antihistamines are still considered a common treatment option for allergic conditions, autoimmune conditions, chronic conditions, and daily symptoms such as itchy skin, skin rash, and nasal congestion.

Individuals who have concerns about the potential side effects of antihistamines should consult with their healthcare provider about their treatment options. A healthcare provider can help weigh the risks and benefits of different types of antihistamines and suggest alternative treatment options if necessary.

Can You Take Antihistamines if You’re Pregnant or Breastfeeding?

It is important to be cautious when taking any medication during pregnancy or while breastfeeding as certain substances may affect the growing fetus or the nursing baby. When it comes to antihistamines, some studies have suggested that certain medications may be associated with an increased risk of certain birth defects. Additionally, certain antihistamines may pass into breast milk and potentially harm a nursing baby. Therefore, it is important to discuss any potential risks with your healthcare provider prior to deciding to take antihistamines.

That being said, there are some antihistamines that are considered to be safe to use during pregnancy or breastfeeding. Typically, second-generation antihistamines, such as loratadine or cetirizine, are preferred over first-generation antihistamines due to their lower risk of sedative effects. However, it is ultimately up to your healthcare provider to determine which antihistamine is right for you, as they will take into account factors such as the severity of your allergy symptoms, any medical conditions you may have, and potential interactions with other medications you may be taking.

In general, be sure to consult with your healthcare provider before taking any medication. It is essential to consider the potential risks and weigh the benefits of taking antihistamines when experiencing allergy symptoms.

What Other Treatments Can You Try for Allergies?

Aside from antihistamines, there are many other treatments available for allergies. Here are some options to consider:

Nasal corticosteroids: These sprays work by reducing inflammation in the nose. They are very effective in relieving symptoms such as congestion, sneezing, and itching. Examples include fluticasone (Flonase), mometasone (Nasonex), and beclomethasone (Qnasl). These nasal sprays are generally considered safe, but it’s best to consult with a healthcare provider before use.

Decongestants: These medications work by shrinking swollen tissue in the nasal passages, relieving congestion. They are available in nasal sprays, such as oxymetazoline (Afrin), and in oral forms, such as pseudoephedrine (Sudafed). It’s important to note that nasal decongestant sprays should not be used for more than three days in a row, as they can cause rebound congestion. Decongestants can also increase blood pressure and heart rate, so it’s best to consult with a healthcare provider before use.

Eye drops: Eye drops can help relieve itchy, watery eyes caused by allergies. They can be either over-the-counter or prescription. Examples include ketotifen (Zaditor), olopatadine (Patanol), and nedocromil (Alocril). Eye drops are generally considered safe, but it’s best to consult with a healthcare provider before use.

Immunotherapy: Immunotherapy, or allergy shots, involves receiving regular injections of allergens to help your body build up a tolerance to them. Over time, this can reduce the severity of allergy symptoms. Immunotherapy can be very effective, but it requires a significant time commitment and can be expensive. It’s important to consult with an allergist to determine if this treatment is right for you.

Supplements: Some supplements may help relieve allergy symptoms, but the evidence supporting their use is limited. Examples include quercetin, butterbur, and spirulina. It’s important to consult with a healthcare provider before taking any supplements, as they can interact with other medications or cause side effects.

Lifestyle Changes: Making lifestyle changes can also help relieve allergy symptoms. For example, reducing exposure to allergy triggers, such as dust and pet dander, can help. It’s also important to maintain a healthy diet and exercise regularly to help manage symptoms. Stress reduction techniques, such as yoga or meditation, may also be helpful.

While there are many treatments available for allergies, it’s important to consult with a healthcare provider or allergist to determine which options are best for you. They can help identify the most effective treatments while minimizing potential side effects.

What Happens if You Stop Taking Antihistamines Daily?

If you have been taking antihistamines daily and would like to stop, it’s important to do so safely to minimize side effects and possible risks. Suddenly stopping antihistamines can result in a resurgence of allergy symptoms, called rebound symptoms, and other uncomfortable side effects such as dry mouth, abdominal pain, and itchy skin, and even withdrawal symptoms including nausea, dizziness, or confusion.

To avoid these symptoms, it is best to taper off gradually by decreasing the amount of medication you take each day. This gives your body time to adjust and prevents sudden withdrawal.

Non-drug allergy treatments like nasal sprays or immunotherapy may be helpful in managing your allergy symptoms before completely stopping antihistamines. Talk to your healthcare provider about safe alternatives that suit your specific needs and allergy conditions.

It’s important to remember that stopping antihistamines shouldn’t be done without proper guidance from a healthcare provider. If you experience any side effects or develop worsening allergy symptoms during this transition, seek medical advice before adjusting your treatment plan.

By working with your healthcare provider and gradually reducing your antihistamine dosage, you can safely stop taking antihistamines without developing uncomfortable side effects or risking potential health complications.

Can You Take Antihistamines if You’re Pregnant or Breastfeeding?

It is important to be cautious when taking any medication during pregnancy or while breastfeeding as certain substances may affect the growing fetus or the nursing baby. When it comes to antihistamines, some studies have suggested that certain medications may be associated with an increased risk of certain birth defects. Additionally, certain antihistamines may pass into breast milk and potentially harm a nursing baby. Therefore, it is important to discuss any potential risks with your healthcare provider prior to deciding to take antihistamines.

That being said, there are some antihistamines that are considered to be safe to use during pregnancy or breastfeeding. Typically, second-generation antihistamines, such as loratadine or cetirizine, are preferred over first-generation antihistamines due to their lower risk of sedative effects. However, it is ultimately up to your healthcare provider to determine which antihistamine is right for you, as they will take into account factors such as the severity of your allergy symptoms, any medical conditions you may have, and potential interactions with other medications you may be taking.

It is important to consult with your healthcare provider before taking any medication. It is essential to consider the potential risks and weigh the benefits of taking antihistamines when experiencing allergy symptoms.

Do Antihistamines Cause Dementia?

Research suggests that long-term use of certain antihistamines, such as diphenhydramine, may increase the risk of developing dementia. Diphenhydramine is a first-generation antihistamine that is known for its sedative effects and is commonly found in over-the-counter sleep aids and allergy medications. A study published in the Journal of the American Medical Association found that adults who regularly took diphenhydramine or other first-generation antihistamines for at least three years had a 63% increased risk of developing dementia compared to those who did not regularly take these medications. The risk was even higher for those who took higher dosages of the medication.

Moreover, studies have also looked into the effects of all antihistamines on mood disorders, including depression and anxiety. While some studies have suggested that certain antihistamines, particularly first-generation ones, may have negative mood effects, others have found no significant association. It is important to note that more research needs to be done in this area to draw strong conclusions.

Can Antihistamines Cause Depression?

Studies have suggested that certain antihistamines may be linked to mood disorders, including depression. However, the connection between antihistamines and depression is still under investigation and requires more research for a better understanding of the relationship.

One study published in The Primary Care Companion for CNS Disorders found a potential association between the use of cetirizine, a second-generation non-sedating antihistamine, and increased depressive symptoms in some patients. Similarly, hydroxyzine, a first-generation sedating antihistamine, has been linked to an increased risk of depression in elderly patients.

It should be noted that these studies have limitations, such as a small sample size and a correlational design that cannot prove causation. More comprehensive studies are needed to better understand the connection between mood disorders and antihistamines.

Long-term use of certain types of antihistamines may also increase the risk of developing depression. This is especially true for first-generation antihistamines, such as diphenhydramine, which have been linked to depressive symptoms in elderly patients.

Despite the potential risks associated with long-term antihistamine use and its potential link to mood disorders like depression, antihistamines are still considered a common treatment option for allergic conditions, autoimmune conditions, chronic conditions, and daily symptoms such as itchy skin, skin rash, and nasal congestion.

Individuals who have concerns about the potential side effects of antihistamines should consult with their healthcare provider about their treatment options. A healthcare provider can help weigh the risks and benefits of different types of antihistamines and suggest alternative treatment options if necessary.

What Other Treatments Can You Try for Allergies?

Aside from antihistamines, there are many other treatments available for allergies. Here are some options to consider:

Nasal corticosteroids: These sprays work by reducing inflammation in the nose. They are very effective in relieving symptoms such as congestion, sneezing, and itching. Examples include fluticasone (Flonase), mometasone (Nasonex), and beclomethasone (Qnasl). These nasal sprays are generally considered safe, but it’s best to consult with a healthcare provider before use.

Decongestants: These medications work by shrinking swollen tissue in the nasal passages, relieving congestion. They are available in nasal sprays, such as oxymetazoline (Afrin), and in oral forms, such as pseudoephedrine (Sudafed). It’s important to note that nasal decongestant sprays should not be used for more than three days in a row, as they can cause rebound congestion. Decongestants can also increase blood pressure and heart rate, so it’s best to consult with a healthcare provider before use.

Eye drops: Eye drops can help relieve itchy, watery eyes caused by allergies. They can be either over-the-counter or prescription. Examples include ketotifen (Zaditor), olopatadine (Patanol), and nedocromil (Alocril). Eye drops are generally considered safe, but it’s best to consult with a healthcare provider before use.

Immunotherapy: Immunotherapy, or allergy shots, involves receiving regular injections of allergens to help your body build up a tolerance to them. Over time, this can reduce the severity of allergy symptoms. Immunotherapy can be very effective, but it requires a significant time commitment and can be expensive. It’s important to consult with an allergist to determine if this treatment is right for you.

Supplements: Some supplements may help relieve allergy symptoms, but the evidence supporting their use is limited. Examples include quercetin, butterbur, and spirulina. It’s important to consult with a healthcare provider before taking any supplements, as they can interact with other medications or cause side effects.

Lifestyle Changes: Making lifestyle changes can also help relieve allergy symptoms. For example, reducing exposure to allergy triggers, such as dust and pet dander, can help. It’s also important to maintain a healthy diet and exercise regularly to help manage symptoms. Stress reduction techniques, such as yoga or meditation, may also be helpful.

While there are many treatments available for allergies, it’s important to consult with a healthcare provider or allergist to determine which options are best for you. They can help identify the most effective treatments while minimizing potential side effects.

What Happens if You Stop Taking Antihistamines Daily?

If you have been taking antihistamines daily and would like to stop, it’s important to do so safely to minimize side effects and possible risks. Suddenly stopping antihistamines can result in a resurgence of allergy symptoms and other uncomfortable side effects such as dry mouth, abdominal pain, and itchy skin.

To avoid these symptoms, it is best to taper off gradually by decreasing the amount of medication you take each day. This gives your body time to adjust and prevents sudden withdrawal.

Non-drug allergy treatments like nasal sprays or immunotherapy may be helpful in managing your allergy symptoms before completely stopping antihistamines. Talk to your healthcare provider about safe alternatives that suit your specific needs and allergy conditions.

It’s important to remember that stopping antihistamines shouldn’t be done without proper guidance from a healthcare provider. If you experience any side effects or develop worsening allergy symptoms during this transition, seek medical advice before adjusting your treatment plan.

By working with your healthcare provider and gradually reducing your antihistamine dosage, you can safely stop taking antihistamines without developing uncomfortable side effects or risking potential health complications.

Frequently Asked Questions

What Happens When You Take Antihistamines for Too Long?
At a minimum, taking large doses over time can result in decreased effectiveness due to the body becoming tolerant to the medication. Continuous use of antihistamines can cause adverse reactions, including drowsiness, dry mouth, dizziness, headaches, and tachycardia. Long-term use can result in heightened chances of contracting certain types of cancers or other health issues.

What are the Dangers of Taking Antihistamines Daily?
Although generally safe on an as-needed basis, taking antihistamines daily may bring about lethargy, dry mouth, lightheadedness, dry eyes, and other symptoms. Moreover, certain antihistamines can have interactions with other medications like sedatives and alcohol which could be hazardous for some people. You should consult with your doctor before taking antihistamines daily.

Is it Bad to Take Antihistamines for Months?
Taking antihistamines for months is generally not recommended as it can lead to side effects such as drowsiness, dizziness, headaches, and decreased alertness. Prolonged use may also cause the drug to become less effective with time. Before taking antihistamines over many months, it is advisable to consult with your doctor to help ensure it’s safe and suitable for your specific needs.

Is it Safe to Take Antihistamines for Years?
Taking antihistamines over a period of years is not considered safe as it can increase the risk of high blood pressure, glaucoma, and the chance of contracting certain types of cancers. It is important to discuss the effects of taking antihistamines over multiple years with your healthcare provider.

Final Thought

Antihistamines are widely available and used to treat a range of symptoms and conditions. When taking them, be sure to understand the class of drug, the possible side effects from long-term use, and try to implement other strategies to manage your allergies in the future.