Is It Safe to Take an Antihistamine for Sleep Every Night?

Antihistamines are often found in over-the-counter sleep aids. From Nytol to Benadryl, many people turn to these medications when sleepless nights start to add up. But how safe is it to use an antihistamine for sleep on a nightly basis?

This in-depth guide explores what the research says, the risks of long-term use, how antihistamines affect the body, and safer alternatives to consider.

Quick Takeaways

• Taking an antihistamine every night for sleep is not considered safe long-term, due to tolerance, next-day drowsiness, and cognitive risks.

• First-generation antihistamines like diphenhydramine can reduce REM sleep and are linked to memory issues and increased dementia risk.

• Safer alternatives include magnesium, herbal sleep aids, and CBT-I, which address the root causes of insomnia without harmful side effects.

What Are Antihistamines?

Antihistamines are a class of drugs that block the effects of histamine, a chemical involved in allergic responses. They’re primarily used to treat:

• Hay fever (seasonal allergic rhinitis)

• Hives and itching

• Allergic conjunctivitis

• Insect bites and stings

There are two main types:

• First-generation antihistamines (e.g., diphenhydramine, chlorphenamine): These cross the blood-brain barrier and cause drowsiness.

• Second-generation antihistamines (e.g., loratadine, cetirizine): These are non-drowsy and less likely to affect the central nervous system.

Sleep aids almost always rely on first-generation antihistamines, due to their sedative properties.

Why Are Antihistamines Used as Sleep Aids?

Because of their sedating effects, first-generation antihistamines are included in many non-prescription sleeping tablets in the UK, such as:

• Nytol Original – contains diphenhydramine

• Sominex – also uses diphenhydramine

• Nytol One-A-Night – uses promethazine hydrochloride

• Benadryl Allergy Relief – contains acrivastine (not typically sedating but sometimes misused)

These medications are easily accessible and often seen as a “safer” alternative to prescription sleeping pills.

Can You Take an Antihistamine Every Night for Sleep?

While taking an antihistamine occasionally for sleep is generally safe for most adults, using one every night raises concerns. According to the NHS and other medical authorities, these medications were not designed for long-term use in sleep management.

Key concerns include:

• Tolerance: The body quickly builds tolerance to antihistamines' sedative effects, often within days.

• Next-day drowsiness: The sedative effect can persist into the following day, impairing cognitive and physical performance.

• Cognitive decline: Long-term use of first-generation antihistamines has been linked to increased risk of dementia.

• Dependency and habit formation: Even though not physically addictive, psychological dependence is possible.

• Anticholinergic burden: Many first-gen antihistamines have anticholinergic effects, which can affect memory, cause confusion in older adults, and impact urinary and gastrointestinal function.

Side Effects of Long-Term Antihistamine Use

Some of the potential side effects of nightly antihistamine use include:

Side Effect	Common With Use?
Dry mouth	Yes
Constipation	Yes
Blurred vision	Sometimes
Dizziness or confusion	Often
Difficulty urinating	Especially in older adults
Memory problems	Possible with long-term use
Increased fall risk in elderly	Yes

In the elderly population, first-generation antihistamines are listed on the Beers Criteria — a guideline used to flag potentially inappropriate medications for older adults.

Antihistamines and Cognitive Health: A Hidden Risk?

Multiple studies suggest a link between long-term use of anticholinergic medications and dementia.

A 2015 study published in JAMA Internal Medicine found that individuals taking higher cumulative doses of anticholinergic drugs like diphenhydramine had a significantly increased risk of dementia over 10 years.

This risk is particularly relevant to people over 60, but even younger individuals should be cautious about habitual use.

Is There a ‘Safe’ Way to Use Antihistamines for Sleep?

If used occasionally (e.g. once or twice per week), antihistamines may be useful during periods of:

• Jet lag

• Stress-induced insomnia

• Temporary shift work transitions

However, for consistent sleep issues, other strategies and supports should be prioritised. Antihistamines should not be the foundation of a long-term sleep routine.

When to Avoid Antihistamines Entirely

It’s important to speak with a GP or pharmacist before taking antihistamines for sleep, especially if any of the following apply:

• Age over 65

• Existing memory or cognitive concerns

• Current use of anticholinergic drugs

• History of urinary retention, glaucoma, or prostate issues

• Use of alcohol or sedating drugs

Alternatives to Antihistamines for Better Sleep

1. Cognitive Behavioural Therapy for Insomnia (CBT-I)

Considered the gold standard by the NHS and NICE guidelines, CBT-I tackles the root causes of sleep difficulties.

2. Melatonin Supplements

Though not available OTC in the UK, melatonin is sometimes prescribed in specific cases, such as for children with ADHD or adults over 55 with primary insomnia.

(Explore our in-depth comparison: Melatonin vs Magnesium: Which Works Better for Sleep?)

3. Magnesium Supplements

Magnesium may help support sleep by regulating GABA and melatonin. It’s especially effective in people with low dietary intake.

4. Valerian Root and Herbal Tablets

UK products like Kalms or herbal teas with valerian, passionflower, or lemon balm offer gentle sleep support.

5. Lifestyle and Sleep Hygiene Changes

• Consistent sleep-wake times

• Limiting blue light before bed

• Avoiding caffeine in the evening

• Creating a cool, dark sleep environment

Should Antihistamines Be Used for Sleep in Children?

The NHS strongly discourages the use of sedating antihistamines for children unless specifically directed by a doctor. They can cause paradoxical agitation and serious side effects in younger age groups.

Can Antihistamines Affect REM Sleep?

Yes, and this is one of the more concerning side effects. Studies suggest that diphenhydramine and similar sedating antihistamines reduce REM sleep, the stage of sleep critical for memory consolidation and emotional regulation.

This could leave individuals feeling groggy, irritable, and cognitively impaired, even after what seemed like a full night of sleep.

Final Verdict: Is It Safe to Take an Antihistamine for Sleep Every Night?

In short: No.

Occasional use may be fine, but taking an antihistamine every night for sleep carries significant risks, especially over time. These include memory issues, increased fall risk, next-day drowsiness, and a possible link to dementia. Antihistamines may help you fall asleep, but they degrade the quality of that sleep.

For persistent sleep issues, address the root cause, not just the symptom. Consider lifestyle adjustments, behavioural therapy, or alternative supplements with fewer long-term risks.

FAQs About Antihistamines and Sleep

Are antihistamines addictive?

They’re not physically addictive, but habitual reliance can develop.

How long can you safely take an antihistamine for sleep?

Can I switch from antihistamines to natural sleep aids?

What’s better for sleep: diphenhydramine or promethazine?