Sleep expert Olivia Arezzolo shares her insights on whether antihistamines should ever be used for sleeping purposes.

Sleep: it’s free. And we all want more of it, so why is it so hard to get? Specifically – that consistent, restorative, uninterrupted, eight-hours-a-night kinda sleep. Which is why we’ve enlisted Sydney-based sleep expert Olivia Arezzolo to solve our myriad of sleep concerns with our Sleep Well Wednesdays series. Check back every fortnight and you’ll be off to the land of nod before you know it.

Last year, I shared the dangers of sleeping pills, some of which you may have already known, like the ‘benzo hangover’.

Similarly, a few weeks ago we shared a doctors perspective on sleeping pills, highlighting how they have addictive properties and lead to tolerance, meaning you need more and more to create the same effect.

However, benzodiazepines aren’t the only sleeping pill to cause major chaos for your mental and physical health, so are over-the-counter antihistamines.

While they do induce drowsiness, and may seem innocent enough, they are far from it, as you’ll soon know. 

1. The sedation lingers the next day, so you’re still exhausted

The primary problem with antihistamines is that the sedative effects of antihistamines don’t just last the evening, they span into the next day.

One clinical paper found even when this was mediated with non-sedating antihistamines in the morning, those taking a sedative antihistamine in the evening were sleepier and more likely to fall asleep throughout the day – compared to those on a placebo. 

2. They contribute to attention difficulties and poor concentration

Most antihistamines contain diphenhydramine, a drug which suppresses the neurotransmitter acetylcholine, which is usually responsible for alertness, learning and memory.

While you aren’t consciously learning or consciously remembering information during sleep, your brain is attempting to do it unconsciously, by transferring information from your short term to long term memory overnight. And, if you have antihistamines running through your body, you compromise this process. 

3. They contribute to brain fog 

After lack of sleep, brain fog is bad enough. No one would willingly add fuel to the fire and exacerbate it, right?

Unfortunately, this is exactly what antihistamines do. They slow your processing speed, which reduces vigilance and leads to that dreaded feeling of brain fog. In fact, the clinical paper mentioned above noted these effects were equal to that of an individual with a brain injury. 

4. They (almost) double your workplace injury risk 

Following up from above, a 2000 study by Georgetown University School of Medicine found those using antihistamines were the most likely of all drug users to have an increased risk of workplace injury, it was 1.5 times higher than non-users.

Concerningly, this study included drug categories of narcotics, antidepressants, antipsychotics and even sedative hypnotics.

The problem with the drug is that although you can suspect the time it will take to exit your body, there is no definitive, one size fits all answer – it depends on your body, what you’ve eaten, health status, if you’ve had stimulants such as caffeine or depressants such as alcohol.

5. You’re a dangerous driver 

A Netherlands study found those under the influence of first generation antihistamines had as great of a driving impairment as one with a blood alcohol concentration of 0.05, technically drunk.

While the study was conducted 3 hours after ingestion of the pill, as above, you can’t be exactly sure when the drug wears off your body, so though your driving performance may not be as bad, it is highly likely it’s still compromised.

Similarly, as highlighted in the 2000 paper above, a study into road accidents in Ontario, Canada, found that those who died due to their own error were 1.5 times more likely to be driving under the influence of antihistamines, compared to drivers not responsible for their fatality.