Benadryl, the brand name for the antihistamine diphenhydramine, is a common over-the-counter (OTC) medication used to treat allergy symptoms, insomnia, and motion sickness. While it is generally safe for short-term use in healthy adults, there are numerous situations where taking Benadryl can be dangerous. Its anticholinergic properties can interfere with various body systems, leading to exacerbated health conditions, adverse drug interactions, and heightened risks in specific populations. Before reaching for this medicine, it is essential to understand the contraindications and precautions outlined below.
Specific Health Conditions
Certain pre-existing medical conditions can be worsened by Benadryl's effects, making its use ill-advised without a doctor's consultation.
Glaucoma
Benadryl is contraindicated for people with narrow-angle or closed-angle glaucoma. The anticholinergic effects can cause the pupils to dilate, which may block the eye's drainage system in susceptible individuals and lead to a sudden, dangerous increase in eye pressure. This can cause severe pain, vision loss, and requires emergency treatment. Open-angle glaucoma, the more common form, is generally not affected.
Enlarged Prostate and Urinary Issues
Men with an enlarged prostate (Benign Prostatic Hyperplasia, or BPH) or other urinary obstruction problems should avoid Benadryl. The medication can worsen symptoms by causing urinary retention, where the bladder is unable to fully empty. This can lead to increased pain, urinary tract infections, and potential kidney issues. Similarly, those with bladder obstruction or other urination difficulties are at increased risk.
Heart Conditions and High Blood Pressure
Individuals with heart disease, high blood pressure (hypertension), or a history of arrhythmia should use caution or avoid Benadryl entirely. The medication can increase heart rate and may cause heart rhythm problems, including QT prolongation. While Benadryl itself does not cause high blood pressure, some combination cold and allergy products containing decongestants can increase blood pressure, compounding the risk.
Respiratory Conditions (Asthma, COPD)
People with respiratory issues like asthma, emphysema, or chronic bronchitis should not take Benadryl. It can dry up the mucus in the lungs, making it thicker and more difficult to clear, which can worsen breathing difficulties. Using Benadryl in these conditions can impede the body's ability to manage respiratory symptoms effectively.
Liver and Kidney Disease
The body processes and eliminates Benadryl through the liver and kidneys. For those with liver or kidney disease, this process is slower, increasing the risk of accumulation and side effects. Healthcare providers may recommend lower doses or alternative medications for individuals with impaired liver or kidney function.
Drug Interactions to Avoid
Combining Benadryl with other drugs can create dangerous additive effects or alter the metabolism of one or both medications. Always check with a pharmacist or doctor before combining medications.
List of Interacting Drug Classes with Benadryl:
- Alcohol: Both are central nervous system (CNS) depressants, leading to excessive drowsiness, dizziness, and impaired motor skills.
- Other Antihistamines: Taking Benadryl with other first-generation antihistamines (e.g., in some cold medicines) or even second-generation ones can heighten sedative effects and increase overdose risk.
- Anticholinergic Medications: Other drugs with anticholinergic properties (e.g., some antidepressants, bladder medications, antipsychotics) intensify side effects like dry mouth, constipation, and confusion.
- Antidepressants: Certain classes like TCAs, SSRIs, SNRIs, and MAOIs can have additive sedative or anticholinergic effects when combined with Benadryl.
- Opioids and Pain Relievers: The combination can lead to severe sedation, respiratory depression, and increased risk of overdose.
- Sedative-Hypnotics: Prescription sleep aids like zolpidem (Ambien) combined with Benadryl can cause extreme drowsiness and confusion.
Safety in Special Populations
Benadryl poses specific risks for certain groups due to differences in metabolism, body composition, and overall health.
Older Adults (65+)
Benadryl is generally not recommended for adults aged 65 and older. This is due to a heightened risk of serious side effects such as confusion, dizziness, increased fall risk, and cognitive impairment. Long-term or regular use has even been associated with an increased risk of dementia.
Children
Benadryl should be used with extreme caution, and under a doctor's guidance, for children. It is not recommended for children under 6 years old. Instead of causing drowsiness, some children experience paradoxical excitation, leading to hyperactivity, agitation, or irritability. Benadryl should never be used to induce sleep in children. Overdose is a significant concern in young children due to their smaller body mass.
Pregnancy and Breastfeeding
While some sources suggest occasional, low-dose use during pregnancy may be safe, Benadryl is not without risk. It can cause premature contractions in high doses and is often not the preferred antihistamine. During breastfeeding, Benadryl is secreted in breast milk and can cause drowsiness and fussiness in the baby. It may also decrease milk supply. Consulting a healthcare provider is essential for pregnant and breastfeeding individuals.
Dangers of Overuse and Misuse
Beyond interactions and contraindications, misuse of Benadryl carries significant risks.
Overdose Risks
Taking more than the recommended dose can be fatal. Symptoms of overdose can range from severe drowsiness and confusion to hallucinations, seizures, irregular heartbeat, and coma. In recent years, social media challenges promoting Benadryl overdose have led to serious consequences, prompting warnings from health authorities.
Long-term Use and Dementia
Chronic, long-term use of anticholinergic medications like Benadryl has been linked to an increased risk of dementia, particularly in older adults. The drug’s impact on acetylcholine, a crucial neurotransmitter for memory and learning, is believed to be the cause. Using the lowest effective dose for the shortest duration possible is the safest approach.
A Safer Alternative: Second-Generation Antihistamines
For those who need long-term or less-sedating allergy relief, second-generation antihistamines are often a better choice. They cross the blood-brain barrier to a much lesser extent, reducing sedative and anticholinergic side effects.
| Feature | Benadryl (Diphenhydramine) | Second-Generation Antihistamines |
|---|---|---|
| Class | First-Generation Antihistamine | Second-Generation Antihistamine |
| Sedation | Causes significant drowsiness | Minimally or non-drowsy |
| Anticholinergic Effects | Prominent (e.g., dry mouth, blurred vision) | Very low or absent |
| Onset | Works quickly (30 min) | Works quickly (e.g., Zyrtec, Claritin) |
| Duration | Short-acting (4-6 hours) | Long-acting (up to 24 hours) |
| Safety Profile | Higher risk for elderly, children | Generally safer for long-term use |
| Example Brands | Benadryl, Nytol | Zyrtec (cetirizine), Claritin (loratadine), Allegra (fexofenadine) |
Conclusion
While Benadryl is a readily available and effective medication for temporary allergy symptoms, its use is not appropriate for everyone. Individuals with conditions such as glaucoma, an enlarged prostate, heart disease, or respiratory issues should avoid it or consult a doctor. Critical drug interactions with alcohol, sedatives, and other medications can lead to dangerous side effects. Special populations, including older adults, children, and those who are pregnant or breastfeeding, face unique risks. For those seeking long-term allergy management, safer, non-drowsy alternatives are widely available. Always prioritize discussing your health history with a pharmacist or healthcare provider before using Benadryl to ensure your safety.
Note: This article is for informational purposes only and does not constitute medical advice. Consult a healthcare professional for personalized guidance. You can find more information from the National Institutes of Health.
