Benadryl is a very common antihistamine that helps relieve symptoms of allergies and hay fever such as itching, rash, and watery eyes. It is typically an over-the-counter, or OTC, medicine. However, in some instances, it is considered a prescription medication when prescribed by doctors with specific instructions for those with more severe allergies. For those who use the drug often, they may experience some Benadryl side effects.
The generic name for Benadryl is diphenhydramine, and although the most common brand name for diphenhydramine is Benadryl, it is also sold as Sominex, Genahist, and Unisom.1
Benadryl is most commonly used as an OTC medicine to dry up areas that have heavy mucus build-up due to conditions such as allergies, the common cold, and hay fever. In some cases, it can also be effective in reducing itching and rashes caused by exposure to allergens.
Benadryl is considered to be safe and effective when taken as prescribed for most people over the age of six to use as needed.
Some people may feel overly relaxed or drowsy after taking this medication, so it is not recommended for use when operating heavy machinery. On average, a proper Benadryl dose is one to two tablets every four to six hours for ages twelve and up. For ages six through twelve, a dose is one tablet every four to six hours. Benadryl is not recommended for children under the age of six.2
In some cases, diphenhydramine may be prescribed as a sleep aid for insomnia due to its propensity for promoting drowsiness. Because of this factor, it can become easy for an addiction to form. It can become a habit to take it every night in an attempt to get to sleep, but this can be extremely harmful.
Most people who develop a dependence on Benadryl develop a psychological addiction, meaning that they begin to believe that it will be impossible for them to fall asleep or stay asleep if they do not take the drug every night.
Eventually, this abuse can cause them to build up a tolerance to the medication which then causes them to take progressively higher dosages to cope with insomnia. This chronic over-medicating can lead to several serious Benadryl side effects such as:
Whereas once the cognitive disturbances and memory loss were believed to be fully reversible, it is now becoming clear that may not be the case. Recently, studies show that there is a link between long-term overuse of sleep aids such as Benadryl and an increase in the chance of developing dementia as an older adult.3
Benadryl is generally considered to be safe for occasional use for allergy relief or to ease a restless night’s sleep. However, some side effects may occur upon use. The majority of Benadryl side effects for occasional use are typically minor and may include:
Some people may experience more severe side effects if they are allergic to Benadryl or other diphenhydramine products. These side effects may also occur due to drug interactions with other medications. These more severe Benadryl side effects can be more concerning and may include:
Benadryl side effects are more likely to occur if a person is taking more than the recommended dose, or if they are taking it regularly for something other than its primary purpose, which is as an antihistamine.4
For those who are prescribed Benadryl as a sleep aid, it is typically not recommended to take it every night. This recommendation is due to its potential for being habit-forming which can lead to increased dosage sizes that are not recommended.
On average, any OTC sleep aid is not recommended to be taken for longer than three days at a time. If a person finds that they need to take it for longer than that due to severe insomnia, then they should speak to their doctor as it may be a sign of a more serious underlying condition.5
Long-term use of Benadryl as a sleep aid can lead to more serious conditions such as liver dysfunction, heart palpitations, intense lucid dreams, hallucinations, and nightmares, and other side effects.
As with any other medication, it is important to consult your doctor about any potential drug interactions that you should be aware of before you begin taking Benadryl. This fact is particularly true if you are taking prescription medications, but it is also something to be aware of with other OTC medicines.
Monoamine oxidase inhibitors (MAOIs) were one of the first types of antidepressants that were developed. Although they have largely been replaced by other medications such as SSRIs, they are still occasionally used for patients when other antidepressants were not effective.
If you are taking MAOIs to manage depression, talk with your doctor before taking Benadryl or other antihistamines as they are well-known to increase severe side effects from both medications when taken together.6
Both Benadryl and alcohol are central nervous system depressants, so you should not take both at the same time or within six hours of each other. Taking both can cause your CNS to slow down too much which can cause motor dysfunction, severe drowsiness, and sedation.
Although barbiturates are not as commonly prescribed today, if you are taking them then you should not take Benadryl without consulting your doctor. Both medications suppress your CNS in the same way that alcohol does, and too much of either can cause severe motor dysfunction, tachycardia, difficulty breathing, and more.
Never take more than one sleep aid at the same time without consulting your doctor. It can exponentially increase your chances of severe and life-threatening side effects particularly in elderly people or those with underlying conditions.