Antihistamines are medications commonly used to treat the symptoms of allergies, including hay fever, conjunctivitis, hives and reactions to insect bites and stings. They also have a number of other legitimate uses, such as treating nausea and sickness, motion sickness and insomnia.

They can also be misused, particularly in forms that can make you feel drowsy. But can you get addicted to antihistamines? We’ll take a look at the possible risks of antihistamine use, including the potential for antihistamine addiction…

What Are Antihistamines?

Histamine is a chemical known as an amine that is found throughout the body and which plays a role in immune response to allergies and a number of other conditions.

Antihistamines are a class of drugs used to treat histamine-mediated conditions. These mainly involve allergies and allergic reactions, but antihistamines that bind to H-2 histamine receptors can also treat upper gastrointestinal conditions that are caused by excessive stomach acid.

Antihistamines are generally divided into two broad categories – those that can cause drowsiness (sedating antihistamines) and those that generally do not. Sedating antihistamines are sometimes used in sleeping aids. They are also sometimes referred to as first-generation antihistamines (those that cause drowsiness) and second-generation antihistamines (those that do not).

Drowsy antihistamines include:

  • Chlorphenamine (Piriton)
  • Cinnarizine
  • Diphenhydramine
  • Hydroxyzine
  • Promethazine

Non-drowsy antihistamines include:

  • Acrivastine
  • Cetirizine
  • Fexofenadine
  • Loratadine

Some antihistamines can be bought in the shop, but others require a doctor’s prescription. They have different brand names and come in many forms, such as capsules, liquids, syrups, creams, lotions, gels, eye drops, and nasal sprays.

Can You Become Addicted to Antihistamines?

In order to answer the question of whether you can become addicted to antihistamines, it’s important to understand what addiction is. There are a number of definitions, but the National Institute on Drug Abuse defines addiction as having a strong and harmful need to use a substance, whether that be alcohol, drugs, or even behaviour, when you know it’s bad for you. It makes you feel like you can’t stop, and it can take over your life.

Addiction is a complex condition and there are a number of different elements. For example, prolonged use can lead to an increased tolerance of the drug, meaning you need to use more and more for the same effect.

Another important element is dependency – which is where your system becomes used to the presence of the drug and comes to depend on it, adjusting your brain chemistry as it does so. When the drug is removed, you can experience a range of unpleasant and sometimes dangerous physical and psychological withdrawal symptoms.

You can also develop a psychological reliance on the drug. In the case of antihistamines, which are sometimes misused for their sedating effects, you could find yourself feeling anxious or unable to sleep without them.

Some antihistamines, particularly those with the strongest sedating effects, are known to be able to cause dependency. Diphenhydramine (or DPH, used in products including Nytol) and Promethazine (or PRN, used in products including Night Nurse) have both been known to cause dependency.5, 6

How People Might Misuse Antihistamines

A recent review of existing studies on the misuse of over-the-counter (OTC) medicines found that this is a growing problem worldwide. However, it can be difficult to provide accurate numbers. Antihistamines, cough/cold medications and decongestants are reportedly the most popular OTC medicines being misused.

Antihistamines are generally misused for their sedating effects. Some people may take much larger than recommended doses in a genuine, if dangerous, effort to combat insomnia or restlessness. Others may use these drugs recreationally. It has also been found that very large doses of antihistamines – particularly DPH – have been used recreationally to produce hallucinogenic effects.

Where antihistamines are misused, it is often in combination with other substances, such as alcohol or opioids, which can increase the risks.

Risks of Misusing Antihistamines

Any medicine can be potentially dangerous, especially if misused or taken in larger doses and situations that are not recommended. Antihistamines are generally safe if taken as directed but side effects of antihistamines that make you drowsy can include:

  • Sleepiness and reduced coordination, reaction speed and judgement.
  • Dry mouth.
  • Blurred vision.
  • Difficulty urinating.

Side effects of non-drowsy antihistamines include:

  • Headache.
  • Dry mouth.
  • Feeling sick.
  • Drowsiness – although this is less common than with sedating antihistamines.

It is always recommended that you do not drive or operate heavy machinery after taking sedating antihistamines.

As already mentioned, misuse of antihistamines can lead to dependency and psychological addiction. It is also possible to overdose on antihistamines. Recent research found that the proportion of drug-related deaths where first-generation antihistamines were detected ‘significantly increased’ between 1999 and 2019. While still rare compared to some other substances, 1,666 samples of antihistamine were detected in 1,537 cases (meaning some had more than one antihistamine in their systems). In more than 85% of cases, the antihistamines involved were available for purchase under pharmacist supervision but without the need for a prescription.9

In the majority of cases, the antihistamines had been taken alongside another central nervous system depressant, including opioids.

How to Safely Use Antihistamines

As with any medicine, antihistamines should only be used as directed. Over-the-counter antihistamines will have instructions and guidance on the packaging and inserts, while guidance will be provided for prescription-only medications containing antihistamines.

The NHS also advises you to speak to a pharmacist or doctor before using any kind of antihistamine if you are pregnant, an older person, taking other medications or have certain other health conditions, including epilepsy, heart, liver or kidney disease.

What to Do If You’re Concerned About Antihistamine Use

If you are concerned about your own antihistamine use or that of someone close to you, it always pays to seek expert help as soon as possible. Your GP can be a good first point of contact as they can signpost you to specialist services.

You can also turn to addiction recovery experts like Ocean Recovery. We have a wealth of experience in helping people to recover from addiction to substances, including alcohol, illegal drugs and prescription or over-the-counter medicines.

Get in touch today to find out how we can help.

John Gillen - Director at Ocean Recovery

John Gillen - Author - Last updated: May 31, 2024

John is one UK’s leading professionals in the addiction recovery industry. Pioneering new treatment techniques such as NAD+ and ongoing research into new therapy techniques such as systematic laser therapy, John is committed to providing the very best treatment for people throughout the UK and Europe. During his extremely busy schedule, John likes to regularly update our blog section with the latest news and trends in the industry to keep visitors to our site as well informed as possible on everything related to addiction treatment.